Thank you for answering all those questions!
Yet, I still have some more: 
- Your music library is using “Plex Music” as its agent and scanner?
- Could you reset your Plex password? (due to Important notice of a potential data breach 24th of August 2022 )
Here is a tool for quick remedy of issues with accessing the server afterwards: You need to reclaim your server, but don't dare to touch the Windows Registry
