As from TFS 2017 Update 1, the traditional “Advanced” access level where to add users with a Test Professional license became deprecated and there’s no way anymore to add/remove users in this access level group.
Advanced access level has been deprecated. Test Manager extension includes all testing capabilities previously part of the advanced access level.
I noticed this caused a bit of confusion where to add new users with the Test Professional license to still provide them access to the advanced test features in TFS on-premises.
The right approach is first to make sure that the Test Manager extension is installed for the Team Project Collection.
Once the extension is installed, you must navigate to the User Hub for the Team Project Collection where you can assign users to the Test Manager extension.
You must install the Test Manager extension for all active Team Project Collections.