Had an interesting case this week where a customer was seeing this window below inside Visual Studio Team Services (VSTS). She was a Project Collection Admin, a Team Project Admin, had a Visual Studio Enterprise subscription active inside VSTS (so she should have had both read and write access inside Test) and the other members of her team saw a list of test plans and cases. It was just her that was seeing this and given all these factors, she should have had the same view as her colleagues.
We verified all the basics - no filters that could be causing the issue and her team had the proper Area Path and Iteration set - but still she only saw this screen below which suggested the team\team project had no tests. We verified as well that she could query for and get a list off all the same test plans and cases her colleagues were seeing in the Test section, but still she was not seeing any there.
Resolution: We had her go directly to a test plan\case URL that we knew was valid (obtained from one of her co-workers), like this: https://<Account>.visualstudio.com/<Team Project>/_testManagement?planId=193&suiteId=194&_a=tests. After she did that her Test section refreshed and her view matched that of her teammates.
We speculate that the issue was created by invalid registry entries for the last selected test plan and plan filter query. In this case going to a valid test plan URL refreshed the registry with the correct setting and showed the filter applied to the test plans. She was able to access the test hub home page afterward.