Sorry @ich777, it was late and I was annoyed. I didn't want to bother anyone with it. Diagnostics attached.
I'm running Epyc 7551P with a Qaudro P5000 and I'm using the official Plex container. I have had this GPU for around 2 years now and I transcode everything to H.265. I've had no problems with transcoding that codec.
The last time I had a HW transcode issues was in February of this year and Plex fixed it with firmware 1.31.1.6733. I used only 1080 movies to replicate my HW issue consistently on the web browser and my Google Pixel 7. With HW on it would only use CPU.
You were right for me. It has worked in the past but suddenly stopped working. At least with HW transcoding enabled. With it off, the CPU transcodes it just fine. But ain't nobody got time for that.
This morning I downloaded both binhex and linxserver's containers and both of those had HW working, but not on my web browser. Only on my phone and NVIDIA Shield (Android). I ended up uninstalling and reinstalling the official container and that solved the HW transcode problem (minus with the web browser).
I kind of noticed that last night. I was looking through the version release history and noticed the past 5 updates have all had fixes dealing with HW transcoding on Linux.
TL;DR - Having issues with HW transcoding and you have all the extra functions setup, uninstall and reinstall the docker container.
johnny5-diagnostics-20231125-1149.zip