The two things to check would be the media itself - not all video plays nice with PP - and the graphics driver.
The same exact video played back perfecly fine 2 weeks ago. The same project too, with no changes at all. I have a Nvida card too and have made no changes to that either. Not sure everything worked a couple weeks ago. Then every once in a while I started having issues, but I could just close and reopen the project and it would be OK. Now, I can't get any vieo at all. If I double click in the monitor box the frame I am on pops up but nothing plays, I just get one frame while audio plays with no issue.
Be that as it may, those are still the two things I'd be checking.