I recently installed Windows 10 Professional (64 bit) when I replaced my hard drive. Now Firefox will not play Youtube video. I get an error that say the browser does not currently support video format. (see screen capture). When I go to the frequently asked questions, it says my browser supports HTML5 video. I have downloaded and installed the newest version of Firefox [56.0.2 (64 bit)] Youtube videos play fine in Chrome and Edge (which is now my default browser until Firefox gets it act together).