Hello @Michaeljep,
When you are starting applications using a Studio it’s working like in kind of a sandbox. You can try a walkaround. Open your registry and navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\Excel\Addins. Check if in Addins key there is node with your Jet addon. If yes, then copy the whole key with your addon to the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\Excel\Addins and also to HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Office\Excel\Addins.
And let’s see if it works.