I take it you’ve been using the Fetch’s “My Media Hub” to stream Plex media via DLNA to your Fetch TV?
If so… you might want to double-check the Plex DLNA settings.
From the related release announcement for Plex Media Server - #296 by Ridley version 1.18.1 (publicly released end of October):
NEW:
- Set the DLNA server feature to be turned off by default. It can be manually re-enabled if required in Plex Web’s server settings (#10530)