Pretty sure @RZ923 covered this a while ago, but I can't seem to find the topic:
When I click into a new part of a lesson, sometimes the video disappears, and I need to refresh the page for it to come back. Using Google Chrome, that I just re-downloaded a few weeks ago (because of other issues).
@the-blade-dancer Probably due to something you did with redownloading Chrome, if it didn't happen before. This never happened to me, so sorry but I can't help.
Make sure all your settings are in check. Try resetting your chrome settings, or even redownloading it again. If you really need to fix this, you can even factory reset your device, though not probably worth it.
I really don't think you should factory reset your computer/phone, but Chrome got a new update...
@divinedolphin Yeah, I definitely wouldn't, but it's still an option. Switching browsers might also work.