Just one of the many mysteries of late is trying to play bits of 'Headlines' video or sometimes Y-Tube. I just get a black screen.
If I have time, I go into FF Tools/Add-ons/plugins and turn off some of the video related things. Then the screen shows - for a while. I then enable the plugins and the whole cycle starts again - but not right away.
I'm not sure if all this started with W10. About then is all I can say, but despite a few issues, years with W7 saw my four computers just work. Day in day out, they would work, and while I deem this last era an investment in catching up with modern computing, sometimes I feel like binning the lot and just have a big jar of pencils like Jeffrey Archer.