When you click on the integrated RWS AppStore in Studio > Add-Ins, Studio crashes with the following error message:

Set property 'System.Windows.ResourceDictionary.Source' threw an exception.

1. Go to: C:\Users\%USERNAME%\AppData\Roaming\SDL\SDL Trados Studio\16\Plugins\Packages 

                      ​​​​​​​C:\Users\%USERNAME%\AppData\Roaming\SDL\SDL Trados Studio\16\Plugins\Unpacked
                      C:\Users\%USERNAME%\AppData\Local\SDL\SDL Trados Studio\16\Plugins\Packages 
                      C:\Users\%USERNAME%\AppData\Local\SDL\SDL Trados Studio\16\Plugins\Unpacked

            If you don't find it there please check also C:\ProgramData\SDL\SDL Trados Studio\16\Plugins\Unpacked 
​​​​​​​                                                                               C:\ProgramData\SDL\SDL Trados Studio\16\Plugins\Packages

      2. Check for the MT Comparison.sdlplugin,  applyTM Template.sdlplugin or LingotekTMS.sdlplugin

      3. Delete the plugin(s)

      4. Open Trados Studio and install the plugin(s) from the integrated AppStore
       Integrated RWS Appstore should be accessible from Trados Studio

Note: If you can't find the path above, open Windows File Explorer, click on View and check "Hidden Items" checkbox.
 

Mismatch between Trados Studio 2021 SR2 and outdated versions of MT Comparison.sdlplugin, applyTM Template.sdlplugin or LingotekTMS.sdlplugin