firefox updated recently and now I am unable to view youtube videos...how do I fix this..i'm running 53.0

What's your computer system?

See if there are updates for your graphics drivers https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration

Youtube currently uses the HTML5 player.

https://support.mozilla.org/en-US/kb/fix-common-audio-and-video-issues

then why does YOUTUBE work on my Chrome browser? I have a HP computer and am running windows 10, 64 bit