I am getting same error now, and when I look at logs I get just 500 errors from an nginx server, not sure which one, locally or remote since the logs are not very clear, but yeah was working fine last night
I can actually bring it back for a short while if I force plex to update my database, but the it seems to break again, most likely when it goes to connect to the servers again
When I reported this issue, I was trying to get to my Plex server locally via an internal IP address on port 32400. The same thing was happening. Plex team MUST really decouple this nonsense of a requirement to talk to their external servers if I want to watch my local content. It’s simple as that.