You Tube videos are not playing

My first post:
Since last week, I haven't been consistently able to play YouTube videos. Just about 30% will play. So, I uninstalled the Adobe Flash player and reinstalled it. Still to no avail. I'm no techie and I need some advice from those who are!

You may have been automatically subscribed to the HTML5 trial program on YouTube. Check here to see if you were opted in:

YouTube HTML5 settings

It works!

I can't thank you all enough for your expertise! It works-yay! yay!
Merry Christmas!