Videos are not working in Firefox

The V.37 version was O.K. for all videos, but after V.38 was installed the video was not working, so I have re-installed V.37. Now it's not working so well.
So I have been using Firefox V.38 again as I said, until today and I have installed V.39.
Both versions won't run the video's for 'YouTube' or other similar app's.
The 'YouTube' app will be working and it will do anything until the actual video is connecting and then only the black screen is viewed (small version), and that's it. The video it's self is without picture or sound, it's the black screen only.
If I do another video it's the same, as is another, and another, and so on.
The 'Chrome' browser is O.K., the video's are working fine.
Can you help me.

To get started, see if there is anything in this document that is helpful:

Flash - MozillaZine Knowledge Base

Did you try with HTML5 yet?

Is it is working, and the Adobe Flash drive is the latest, and Java is working, etc.
I don't now what it is.

mikeholdsworth said:

Is it is working, and the Adobe Flash drive is the latest, and Java is working, etc.
I don't now what it is.

"Is it is working..." What does that mean?

Java has nothing whatsoever to do with this, but javascript, a totally different item, may.

You may have the latest Flash drive installed, but did you use the Adobe Flash removal program first, before updating Flash itself?

https://helpx.adobe.com/flash-player...r-windows.html

A quick test: Start Firefox in Safe Mode, to ascertain if, perhaps, there is an extension that is interfering with Flash.

Safe Mode - MozillaZine Knowledge Base

I have already checked, the hardware accelerator is not working.
And I've done the Firefox in Save Mode, there isn't.
Thank you both, I'm still waiting and so is RolandJS, I assume.