Today there was an Android System Webview update in the Google store on the Shield. It mentioned bug fixes and speed improvements. When installed everything worked again.
I’ve just tried this and the problem still exists … just to make sure, I also restarted the Nvidia.
When I open Plex and go to settings, under the section “Plex Media Server”, I cannot see the icon which shows the status of the server, so I cannot even attempt to start it.
Also to confirm, the OS version is 8.2.3 [32.6.518.0] with no further updates available.