I just had a recurrence of this issue with 1.29.0.6244 installed on Mojave.
I had not made any changes to the install, the only factor was a change of external (ISP provided) IP address.
I followed the instructions in Server settings are unavailable after last update. MacOS - #50 by nibbles
That thread has now been closed. The Plex staff member posted a notification that the issue has been resolved in version 1.30.0.xxxx
It appeared to work, I had access to my server settings on 1.29.0.6244. So I upgraded to the latest version (1.30.0.xxxx) which included the update notes about fixing the issue.
I have lost access to my server again. This is getting infuriating, hopefully following the instructions one more time will resolve the issue permanently.
