What version of Plex Media Server are you running?
You need to be at 1.19.2.2711 or later. See thread below for details.
I’m not sure what else to check. Maybe others can assist.
As mentioned in the thread, the Plex client for your TV is 3rd party and no longer supported. It will eventually irreparably break. Might be time to consider using a Roku/FireStick 4K/etc. The client will be much faster and more responsive as it has a current CPU. Also, you’ll pick up new features such as Skip Intro for TV shows. HEVC video will also direct play. 4K HDR compatible Rokus & FireSticks run about $50 USD. Amazon frequently puts their FireSticks on sale for $10-$15 USD off list. Not sure how often Rokus go on sale, but they do sell refurbished version on Amazon for a discount.
