Server Version#: 1.21.3.4021
There was this very old bug about setup exposed only through custom domain not playing nice with plex (i.e. Remote access: incorrect status check - Plex Media Server / Remote Access - Plex Forum)
When reading Plex Media Server - #397 by rcombs I had high hopes that it was finally fixed, but not quite:
- The remote access test feature is flaky. Sometime it says green, sometime it says red
- Sonos integration does not work at all with the custom domain. It needs your system to be exposed through the plex.direct address