I have exactly the same problem - tbh that happens all the time when you guys update the app. Also i have updated all those drivers yesterday: HEVC, LAV - just about everything and it still doesn't work, Switching the playback engine does absolutely nothing. I always dread the update days on SLR, usually the app is done after an update. Seems a clear case of: do not update if it's not broken...
Also a lot of people complain about that exact issue on the oculus store. Basically half the comments are about it not working after an update..
Any ideas how i can get the app back to play slr videos again? For examples you can use any VR Edging scene in 4k to see the error, in fact not a single of my downloaded videos is running on the DeoVR app.