Server Version#: 1.40.3.8555
Player Version#: 4.129.1
As well as the latest ROKU version
After upgrading to this latest version of the PMS server (Windows Platform), Plex no longer plays subtitles. This is not my media issue as subtitles play fine on JellyFin. This is Plex issue (the latest upgrade).
There is really nothing else to say here. What happened to quality control before releasing your product?