UPDATE: I tried reinstalling Windows to see if there was like a corrupt file. I had to reinstall all my drivers and this time I thought I'd go with Firefox version 45.0.1 as a clean install. Still however the problem persists. As soon I log in to my Facebook account and scroll to a video, the video thumbnail shows but just doesn't play. I again tried the flash video downloader add-on to force flash to play but still no response. Once again I've always been an avid Firefox user and DO NOT want to switch to another browser just to play videos on Facebook,