Looks like Plex pushed out a bad update and it appears to have bombed Plex on some Vizio TVs according to me, and the Plex Forums.
On my Vizio 705x-H1 I suddenly started getting that Plex was taking a long time to start. Rebooted the TV, cleared Plex data, nope. My Shield, Androids, M50 upstairs, web pages, etc all worked without a problem
Issue appears to have been bad code pushed, revoked, and cached.
Currently not fixed for me, or wasn’t 12 minutes ago, but hopefully in a bit. It’s not your Vizio evidently, it’s cached code. #ConnectedProblems
Also appears to have affected WebOS, LG, some other brands based on this Reddit thread