I am using Firefox with the latest update which installed just a few hours ago and an update to Windows 10 as well. So, I am up to date. All videos, no matter who posted them, including mine are broken. I don't even have the media player showing up.  Everything was working before, so it is something in the code...

Montgomery Scott, Engineer on the Enterprise once said " The more they overthink the plumbing, the easier it is to stop up the drain..."

You have plugged up the drain, Get some Mr. Plumber or Draino.  :)