Lync for Mac (OSX Yosemite) Sign-in Fails Repeatedly

If you were brave enough to upgrade your Mac to OSX Yosemite (beta) and your Lync for Office 2011 (with Office 365 or Lync on premise) no longer will sign in, the potential fix is listed below. 

Primary Symptom: when you attempt to log into Lync, it appears to sign you in just fine, but after briefly displaying your Lync contacts, it immediately signs you out and gives you a generic error message that either the server is unavailable or some unknown error has occured. 

Likely Resolution:

  • Make sure you have all Mac for Office updates and are running the very latest updates
  • Go into Settings (System Preferences), Language & Region
  • Change the language from "English-Primary" (or whatever the language is set to) to "English-US" 
  • Reboot
  • Go back into Settings (System Preferences), Language & Region
  • Change the language back to "English-Primary"
  • Reboot
  • Open Lync and you should be able to log in just fine this time
Thanks to Tiago for updating me, the fix for this issue is being released by Microsoft today; see the official Support KB below related to the known issue: 
Hopefully this will resolve your issue once and for all, as we all eagerly await Mac for Office '16 πŸ™‚ 
Thanks to the Lync team for providing us with a fix for this issue...see the KB article and download the update now!
Comments (93)

  1. Anonymous says:

    no worky for me πŸ™ symptoms the same.

  2. davidbaliles says:

    Sorry to hear it…try toggling the languages back and forth but make sure you do a full reboot after each.

  3. Anonymous says:

    The error I was making was setting the language… I didn't realize you had to drag the language to the top of the UI… I was just clicking it

    thank you thank you thank you

  4. davidbaliles says:

    Glad to hear it πŸ™‚

  5. Anonymous says:

    Wow! That's a weird workaround, but it works! Thanks for posting this!!!

  6. Anonymous says:

    Thx. Strange workaround but work's for me too.

  7. Anonymous says:

    Thank you for the tip. I tried 4-5 other workarounds so far which didn't do the trick. This one did…

  8. Anonymous says:

    Thanks!! I've been struggling with this for a while, but this worked like a champ!

  9. Anonymous says:

    Thanks! This worked for me!

  10. Anonymous says:

    Works like a charm! Thanks a lot =)

    Lync 14.0.9 was also failing to login, don't forget to click&drag the language to top of the list.

  11. Anonymous says:

    This solution worked after low and high level troubleshooting failed.

    Google-fu led me to this dojo.

    Thank you, Mr. Baliles.

  12. Anonymous says:

    Thank you very much, Sir! I updated this evening and would be in hot water if I wasn't able to log into Lync for tomorrow's work day.

    Thanks again for posting this!

  13. Anonymous says:

    You said to "Go into Settings…" but where do I find "Settings"? Is this within Lync?

  14. davidbaliles says:

    Settings on your Mac, within OSX…not within Lync client. OSX calls it "System Preferences" Gear icon in your doc.

  15. Anonymous says:

    Got it — and it worked! Thanks so much, how did you ever figure this one out??!

  16. davidbaliles says:

    Lots of trolling and trial & error πŸ™‚ I'm glad it worked for you!

  17. Anonymous says:
    • thank you very much 0 workaround worked for me too.
  18. Anonymous says:

    Dave you absolute star!!! This worked first time!!! πŸ˜€

  19. Anonymous says:

    And another happy customer. It did work for me as well.

  20. Anonymous says:

    Thanks. Switching the language in System Preference solved my problem

  21. Anonymous says:

    worked like a champ for me.

  22. Anonymous says:

    not its working fine, thanks!

  23. Anonymous says:

    Thanks so much for this bizarre fix. πŸ™‚

  24. Anonymous says:

    It worked! Please, Microsoft, show you are improving and fix it soon, I speak spanish and solutions like these are a pain.

  25. Anonymous says:

    Ridiculous work around…

    It works – don't get me wrong, but why the hell have Microsoft not addressed the issue?!?!

    Very intrigued as to how you came to find or work out this fix πŸ˜‰

  26. Anonymous says:

    Wow, how odd… this totally resolved it.  Thanks!

  27. Anonymous says:

    Worked great! Thanks!!

  28. Anonymous says:

    Thanks, this does it, although i had to try this a few times, keep Lync open while changing the language preferences.

    Finally , my Lync status messages are in Spanish, but I can live with it.

  29. Anonymous says:

    Worked like a charm… Thanks!

  30. Anonymous says:

    This worked.  First time.  10/10!

  31. Anonymous says:

    Thanks for this solution… got me up and running. Though I hope it's resolved soon in an app update as it's definitely not a good enterprise fix! It's been a known issue since June! –>

  32. Anonymous says:

    Nicely done Man!  Doesn't make sense, but it friggen worked!  Cheers!

  33. Anonymous says:

    I can't be the only one curious about what change is being made here: is there some difference in encoding that Lync needs to display or something?  Anyhow thanks very much for the fix, I'd been running my Lync client in a windows 7 vm during the public beta and it was getting very old.

  34. Anonymous says:

    Took a bunch of changing back and forth, but it does work.  I did not need to complete the reboot step as Lync seems to recognize the language change without it.

  35. Anonymous says:

    Thank you!!  Worked perfectly as you outlined – will share with others on my team!

  36. Anonymous says:

    This strange workaround actually works!

  37. davidbaliles says:

    For those of you who it's not working for…I had the same behavior when I first did this. A couple of things to try…OSx Yosemite now differentiates between English and English U.S. If you're using another language, please add both of these, and pivot between these two, with reboots in between. Sometimes the reboot isn't required, but in my case it was. Also, if you've flipped between Language 1 and Language 2, then back to Language 1, and it still doesn't work, try reverting back to your native language and reboot. USUALLY the above method works, and I guarantee if you try enough language switching combos, it will resolve the issue for you. Sadly, I'm not knowledgeable or in control of why this is the workaround, but it appears to be introduced soley with Yosemite's language packs. I'm sure Lync client for Mac will receive an update to work around the change in Yosemite, but until then, this is the only fix I've been able to arrive at. I hope this helps the few of you whom my workaround isn't working for. Cheers!

  38. James AV says:

    Thank you David! It worked on one of my Macs but doesn't want to work on the other one despite the many times I switched between the two English languages.

    A quick one for you: any chance to obtain the same thing through the Terminal or by copying some files from one folder to another?

    Basically, I have the feeling that if you manage to find a Terminal based solution it will be more effective…

    Thank you again for the great job. You're a star!

  39. Anonymous says:

    Thanks! This work-a-round was very helpful.

  40. Anonymous says:

    Took me about four goes with different versions of English. My target is English UK and I had to add English US. Toggling between them with reboots didn't seem to work but then I found plain 'English' and switching to that cracked it. Great relief all round. I'll share this with my colleagues. Thank you.

  41. Anonymous says:

    OSX 10.10 (original Yosemite)

    LYNC 14.0.9 (140606).

    Was initially getting the "sign-in but immediately sign out again" loop.

    Original System Preference "Language and Region" setting: English (English – Primary) [ only 1 item in list ]

    Added English US, deleted English (making English US – Primary).

    Upon trying to exit System preferences, I was asked if I wanted to reboot, so I did.

    After Reboot, I re-added English , and deleted English US.

    Upon trying to exit System preferences, I was (once again) asked if I wanted to reboot, so I did.

    After Reboot, LYNC started, and did not "loop". I will note that it seemed to take ages (over a minute) to update the status of my contacts. Can only presume something (cached) was being re-built under the covers.

    But success for me. Thanks for the original thread David.



  42. Anonymous says:

    I followed exactly what is explained.It works. Thanks for your help.

  43. Anonymous says:

    Worked !! Thnak you David.. you're a star.

  44. Anonymous says:

    That has got to be one of the weirder workaround in a while ☺

    But, it works! Thanks, David!


  45. Anonymous says:

    hello, from french user… all swaps were unsuccesful BUT sticking on plain english works fine !

    not a problem, office is in french and keyboard ok too…. only yosemite menus in english, not a big deal !

    ouf…. without lync i would have to revert to mavericks…

  46. Anonymous says:

    Worked like a charm. Great find.

  47. Anonymous says:

    This worked for me after installing the final release of Yosemite. Thank you so much for this info!

  48. Anonymous says:

    To Aussie JD – thanks man (and original post!) – I followed the antipodean steps and worked a charm!

  49. Δ°rfan Nuri Karaca says:

    Thanks a lot, yosemite release run me into this problem today but i am back, thanks to you πŸ™‚

  50. Anonymous says:

    Worked for me … you saved my day!

  51. Anonymous says:

    Thanks!  it worked.  our IT sent out a note telling us NOT to upgrade.  of course I missed it.  and when I realized that Lync no longer work, I though I am surely in trouble.  Thanks for the fix!!

  52. Anonymous says:

    Wow. That worked! Bizzare or what? Thanks πŸ™‚

  53. Anonymous says:

    Worked for me! iMac (27-inch, Late 2013)

  54. Anonymous says:

    So strange, don't skip any steps….but it absolutely did the trick.  

    Thank you!

  55. Anonymous says:

    it worked! I'd love to hear how you found this work around….  it not a logical step.. so I assume you have some lync insight?

  56. Anonymous says:

    Worked for me too, Thanks!

  57. Anonymous says:

    tks a lot, perfect! Work for me…

  58. davidbaliles says:

    Part of the issue here also seems to relate to the introduction of a non-English UK and non-English US language. One or the other is fine, but the "agnostic language" appears to throw a kink into Lync…who knew! Hopefully Office for Mac end of 2014 will update more than this bug and bring the Yosemite experience for Office users closer to the Windows version!

  59. EeKay says:

    Works fine: drag another language on top in the languages preference pane and reboot. Then drag english back on top and reboot… restart Lync and voila πŸ™‚

  60. Anonymous says:

    Worked for me!  Life saver since I work at home.

  61. Anonymous says:

    Yes, weird but worked. Thanks!

  62. Anonymous says:

    Hi Bro,

    This worked just fine for me. Thank you very much!!!

  63. Anonymous says:

    Very strange problem, but fortunately the workaround did work for me.

  64. prettyby7 says:


    Very weird and don't see the connection, but worked like a charm!

  65. Anonymous says:

    Groso, me anduvo ok. Gracia maquina.

  66. Anonymous says:

    Worked great. Thank you!

  67. Anonymous says:

    Worked for me too

  68. Anonymous says:

    Thank you! I wasted two hours clearing cache and preferences and doing all the logical things before it hit me like a ton of bricks that I had upgraded the OS!  Duh!  But like others, I am astounded that you or someone found this. It's not exactly obvious that a language issue would cause this symptom, and since the net of changing the languages is exactly zero, it couldn't possibly fix anything … but it did!

  69. Anonymous says:

    Worked like a charm for me.

    Thank you so much!


  70. Anonymous says:

    This worked for me – thankyou !

  71. Anonymous says:

    Worked for me as well, however – only when changing back to ENGLISH-ENGLISH language – as I am german… it won't work if you change back to German language – you get into the same loop again…

    Thanks for the hint !!! much appreciated

  72. Anonymous says:

    Adding another language (in my case spanish) worked!  Thanks.

  73. Anonymous says:

    Lync for Mac 14.0.10 will be coming out before the end of October which will include support for Yosemite as well as other fixes and functionality.

    Terry Adams


  74. Anonymous says:

    Thank you for the work around!!

  75. davidbaliles says:

    Thanks for the update Terry! I know everyone's looking forward to it πŸ™‚

  76. Anonymous says:

    Thanks getting this possible fix posted. Worked great! One small note..  I didn't need the reboot, I just removed English US as primary and then added it back.

  77. Anonymous says:

    ive tried and tried and tried, and it didnt helped. then i began thinking around and changed the keyboard layout to english, and that did the trick. my systemlanguage is german

  78. Anonymous says:

    Thanx David for this life saving information. Got Lync working in 2 minutes before one ow my daily 4-5 Lync meetings πŸ™‚

  79. Anonymous says:

    thanks, this works also with setting in Dutch language. switch to English US, reboot, then to English, reboot and Lync works again. hope I can switch back to Dutch with the coming update.

  80. Anonymous says:

    Thanks! It worked for me, now just need an outlook fix!

  81. Anonymous says:

    Thanks! Worked for me.

  82. Anonymous says:

    Wow.  Craziest fix ever.  Winner.  Thanks

  83. Anonymous says:

    Worked for me today. Thanks so much.

  84. Anonymous says:

    It works for me as well. Thank you very much for sharing.

  85. Anonymous says:

    It works!

  86. Anonymous says:

    Brilliant David! thank you

  87. Anonymous says:

    Thanks! I deleted English-Primary and add English-US Primary. reboot.

    deleted English-US Primary and add English-Primary.

    and then it solved.

  88. Anonymous says:

    Oh…. good tips!  It works for me!  Thank you, David.

  89. Tiago Rôxo says:

    We will have the final fix today(28/10/2014)!…/3012202

  90. Anonymous says:

    Thank you ever so much! This one was a b**ch to figure out! I almost threw Yosemite back out. Mine was a switch from the English Primary to Norwegian – reboot – switch back to English primary – reboot – apply huge smile on face. You deserve a cold one!

  91. Anonymous says:

    Thank you very much. It saved me from going back to Mavericks.

  92. Anonymous says:

    YOU ARE MY HERO. Thanks so much

  93. Anonymous says:

    Wow,…. nice to see they were paying attention.  Thanks for the Writeup and links.

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