Lync Error: "Cannot Sign into Lync" or "The sign-in address was not found"


One possible solution which is to refresh Lync cached endpoints. 

When Lync 2010 connects to a specific front-end server, it caches that endpoint to make the sign-in process faster in the future. However, sometimes the endpoint can be changed which can cause your user sign-in to fail. To delete the endpoint cache, follow these steps:

Locate the local application data folder:

Windows Vista and Windows 7: %LOCALAPPDATA%\Microsoft\Communicator\<sip_address@contoso.com>\

Windows XP: %USERPROFILE%\Local Settings\Application Data\Microsoft\Communicator\<sip_address@contoso.com>\

Delete the file that is named EndpointConfiguration.CACHE.

Restart Lync 2010, and then try to sign in to Lync Online.

Comments (3)

  1. Dhruv Sachdeva. says:

    It is still not working.Not able to sign using my credentials but if i enter someone else credentials it work.Dont know why

  2. mohammed asif says:

    i install Lync 2010 in admin log in then log in admin account……

    when log off and log in domain and can't sign in in domain…..

  3. yoes says:

    got the same issue. my solution was install lync basic 2013.