Having the same issue on Android (Fire tablets) as well…It’s unusable in this condition.
I’m on the internet, I’m able to download updates and apps, but the Plex app keeps telling me it can’t authenticate. My phone app works, it’s also Android, so this issue is really strange…
So, I found a work around (for me). I originally had a plex account with a gmail address. I never signed into plex using the “use google” setting before. I always used the “sign in with a plex account” option (because when I started using plex the gmail option didn’t exist). I just did the “google” option and it let me right in. How are you signing in?
I’m using the “sign in with Plex”. I have a Plexpass account (have for years) so I’ve not tried “sign in with Google” I just figured that would be a different account. That it wouldn’t authentic to my Plexpass. Moreover, I’m not keen to let Google into another aspect of my life.
I have a Plexpass account, had it for about 10 years or so, I always signed in via the “sign in with Plex” in the past. It does happen to be tied to the same gmail account. Just to try it, I logged in with Google, it moved me right though and connected to my server.