You’ll need to read, in detail, the posts and comments (in order), as a lot has been happening over the past few months.
If you have PMS 1.29.xx, transcoding should be working… Then after that there were a few versions that had issues. This went on for a few months, until things started to work again.
If you’re using a regular bare-metal Linux, or VM, the main thing is to upgrade to a more recent version of PMS (1.31.3.6819 + 1.31.3.6868) is where things start to work, and strip out all Nvidia drivers stuff and install 525.x… Flushing out all the old NVidia driver stuff can be crucial before you upgrading it again, and many folk get this wrong and wonder why they have issues.
Here’s my forum post, where we go over a few things and I finally posted up the PMS version that worked. My post went on a wild goose-chase, as using the Chrome client caused me nothing but problems and we later found it this was a different fault in PMS - this rendered some of my tests useless! But it’s all worth a read 
