Couldn't find a way to get the TFS extension to on-premise TFS server, it always finding the VSTS account only. we are not using VSTS. Also tried https://www.visualstudio.com/en-us/docs/marketplace/get-tfs-extensions from step 3 its different.
all the time it market place find vsts account. its of no use. Any help ?
The Test Manger extension could be installed for VSTS and TFS 2017 and upper version.
But for TFS 2015, it doesn't need to installed it separately. In TFS 2015 and TFS 2013, to get the test manager features, you should change the Access Level of your uses to Advanced.
Login in to the Access level page, usually the path is http://servename:8080/tfs/_admin/_licenses
Note: You could also set the Advanced access level to default.