It's a possibility, but tons of users watch YouTube without any issues using ad blockers, so my guess is that it's something else.

An easy way to test is to run Firefox in Safe Mode. This will temporarily disable your browser extensions (like your ad blocker).

If the issue is not present in Safe Mode, it could be caused by your ad blocker. However, it could also be caused by hardware acceleration, so you may want to try disabling hardware acceleration when you return to normal mode if the issue wasn't happening in Firefox.

If none of that helps, go to the YouTube HTML5 test page and let us know if you see any red exclamation marks next to any of the video codecs listed. It can be normal for the MSE & WebM VP9 one to have that, but the rest of them (particularly H.264 and MSE & H.264) should display blue check marks.

Hope this helps.

Video's show pictures in Safe Mode and I disabled hardware acceleration only to have no picture just sound on the video's so that means it's the ad block. Any chance this can be fixed or will my donations be for something I can't use?

Colorado2019 said

Video's show pictures in Safe Mode and I disabled hardware acceleration only to have no picture just sound on the video's so that means it's the ad block. Any chance this can be fixed or will my donations be for something I can't use?

Hello Colorado2019,

If your adblocker causes a problem, that is not something Firefox should (or even could) fix ....

The adblocker you have installed ("AdBlock 3.30.0"), isn't even on the official addons.mozilla.org page - you could try to contact their support.

Also see this article :

https://www.lifewire.com/youtube-black-screen-4178316

and :

https://www.lifewire.com/fix-youtube-videos-that-are-not-playing-4178790