Using my backup Plex Media Server v1.7.x I've got a happily running RPi3 using the latest PMP embedded.
However, when using my main server running PMS 1.8.x, the video playback resolution is stuck on 480x270. I can't work out why, and it's pretty annoying as you can imagine!
Everything else looks to work fine, all the menu's etc are full/max resolution, it's just video playback resolution that's stuck. Changing the media container, or manually forcing the client to output a higher native resolution doesn't help, it's still displays the min.
The older PMP client (v1.7?) has the same issue, it's only using my backup PMS with v1.7.x that works ok. I'm aware this indicates a setting, profile or something else wrong with the PMS running 1.8.x but everything is set to 'max', with even the remote internet option set to Original Quality (in case it was using remote failback).
Thanks for the help, please ask any Q's !