No idea. It just worked. Only thing I can suggest is basic troubleshooting: a) make sure you’ve the latest version of the Plex client (Authorized Devices, SmartTV Announcements); and b) turn off TV then remove power cord for 20 - 30 seconds. Power button on remote just puts TV into a deep sleep. Pulling the power cord forces a full power off. This will force the TV to reload the app the next time you launch it, instead of possibly just bringing it out of background / sleep status.
I have not used the LG client in several months. It would not play PGS/VOBSUB subtitles without transcoding, and HDMI-ARC limitations meant no TrueHD or dts-HD audio. I now have a Nvidia Shield connected directly to my receiver. No Dolby Vision support, but all my Plex HDR content (outside of demo videos) is HDR10 anyway, so not an issue for me.
