Yep, definitely an SSL Certificate issue - if I open the web browser on the TV and visit https://plex.tv/ I get an SSL Certificate error. This should work without errors and on my Windows 10 PC, its fine.
The old certificate was a Digicert certificate, expiring on 14 June, so the team have obviously swapped that out ahead of its expiry. They’ve moved to Lets Encrypt, which doesn’t have the greatest compatibility. Worse, Lets Encrypt is currently using a root certificate that expires 1 October 2021, so if this hasn’t already broken for you, it probably will shortly.
This might be worth reading for some background info - https://www.tomsguide.com/news/smart-home-cert-disaster
Probably need to look at installing the root certificate manually, but I think that’ll require rooting the TV.
