I had the SAME PROBLEM!! I TRIED EVERYTHING TO FIX IT....THIS IS THE ONLY THING THAT WORKED!
I checked many times to make sure all my "settings" were right....they were.
I tried uninstalling and reinstalling both java and all adobe software TWICE....I even disabled my internet security in case it was some ad-blocker problem...still, it would not work.
THIS WORKED...and although you probably think you already did this, TRY THESE LINKS....THEY HELPED ME.
The first one to go to to unisntall JUST THE FLASH PLAYER ONLY is:
Then you have to reinstall the FLASH PLAYER by going to:
This really did work. I was pleasantly surprised after spending an entire afternoon trying to find out why I couldn't play flash videos although my java was turned on and I had all the latest updates. Hope this helps you, too!!!