Thanks for your help everyone. I figured out my problem. Apparently, one of my Chrome extensions was blocking the videos. It was Pocket Universe, which makes no sense (it's not supposed to block videos). But after I disabled it, the videos load now. I contacted Pocket Universe and they're confused too.
(As for mobile, it still doesn't work. Maybe my phone just can't handle big resolutions.)
Anyway, my problem is resolved now (other than on mobile)