No image on YouTube!!

Use ResetBrowser to clean up

Clear the cache and cookies like this

For hardware acceleration, I need the name of your browser.

For Flash Player, the latest version is here

To update your graphics card driver, you can check it with DriversCloud

For a potential infection:
-Run AdwCleaner

A ad blocker or a security feature (such as your antivirus: firewall rule) could also be the cause.

With these brief answers, you should be able to identify the source of your problem.
A+

I did: resetBrowser - clean cache and cookies - check Flash Player - DriversCloud and AdwCleaner
All of this, foolishly because I know nothing about it
I just watched 3 videos on YouTube and it works!!!
How, why, I have no idea, but anyway, thank you Pistouri!!!!!

Don't try to understand, anyway it's very good that you tried and tested the procedures
Happy for you to have the images (the video) with sound on YouTube :-)
You can close the discussion like this
Good luck
Have a nice day.

--
pistouri

Thank you again!!!!