An issue with part of the infrastructure was identified yesterday and fixed. The issue was affecting PMS connectivity tests for remote access in some regions. It was definitely affecting Europe-West region.
If there are still issues, would like to see server logs captured some minutes after loading the server settings page for remote access in a browser and doing an F5 browser refresh.
(of course ensuring debug logging was enabled on the server previously)
See
https://support.plex.tv/articles/201643703-reporting-issues-with-plex-media-server/
https://support.plex.tv/articles/200250417-plex-media-server-log-files/
