Skype 2019 MACP Stopped Working - User has insufficient permissions

We have been using the Skyp 2019 MACP for some time without any issues. When we first set it up, we had the error message "User has insufficient permissions" but were able to resolve it by installing OData and running bootstrapper.exe. I'm not sure what is causing it this time, I ran the bootstrapper.exe again but that did not change anything. 

Does anyone know what could be causing this issue, or where we should look (our Skype Admin has moved on and we haven't found a replacement).

Thanks!

John