Changing the installation from Machine based install to User Based install you must delete the FTA key manualy or with a script.

The HKCU key(new)

[HKEY_CURRENT_USER\SOFTWARE\Classes\CLSID{00425F68-FFC1-445F-8EDF-EF78B84BA1C7}\LocalServer]
@=”C:\Users\<Username>\AppData\Local\Microsoft\Teams\current\Teams.exe”

Solution.

Delete the reykey before installation of one other installation, otherwise the FTA is not working correct