It seems like I simply can't play MP4s anymore in Firefox...specifically when I open them in their own tab. Either they will appear as a blank box, or they will play for about a second then pause and become unresponsive, or it will give me the error message "video format or MIME type is not supported". Basically it will error out in a dozen different ways, but the result is always that I CAN'T WATCH THE VIDEO!

I tried googling, but all the top search results were from 2015, and their suggestions didn't work. I also updated my video card drivers, but that didn't change anything. Furthermore if I ever try a video that doesn't work on FF on Chrome it will work perfectly so the issue is specifically with FF. I'm seriously getting tired of this problem, please help!