Suddenly no remote access

Hi there, similar issues to the other posters - plex had been happily working for a long time, now it is not. Remote access enabled, local page shows it’s available on specified port. Tried changing specified port with no joy. Unlinked and re-linked server to account, no joy either. Please could you assist?

EDIT: Nothing worked, other than accessing the (working) port via the browser on the external IP address and linking the server from that address - e.g. https://PUBLICIPADDRESS:32400

Some sort of bug?

EDIT2: This worked once, but did not survive a server restart, so clearly isn’t the way to go. Please assist?