Ok so I’m running Plex on Fedora 33. PMS is on Version 1.21.1.3876. One of my remote users is on a PS3. About a week ago they stopped being able to connect. Currently their device says that it’s trying to connect to the private IP of my Plex server on my local network (192.168.1.xxx) rather than trying to point to my public IP.
Random thoughts — I am not an expert with PMS forwarding.
I assume your PMS is on your private subnet. As such did your ISP IP address change which is quite common?
iMHO — exposing PMS on the internet might be problematic unless you setup a dynamic DNS server which your router keeps updated, but I am not a Dynamic DNS expert.
Are you able to validate, via the internet, on one of your local devices to PMS? I am hoping that the process of doing this might fix your issue but…
Have you tried rebooting your PMS server and possibly the host it is on?