That has been an issue for some weeks and youtube apparently keeps changing how it works. There is an ongoing thread on Reddit (first link below). In the second link, a user script is mentioned; to use that you have to install Greasemonkey or one of the other monkey extensions. (You need to remove the blank space in the Reddit links.)

https://www.reddit. com/r/uBlockOrigin/comments/178yasm/ https://www.reddit. com/r/firefox/comments/17caygd/anyone_else_getting_this_on_using_ublock_origin/

• https://addons.mozilla.org/firefox/addon/greasemonkey/

sorry, doesn´t say me anything.

I have not installed any ad block. So, what shall I uninstall? Michael

You can check for issues with Enhanced Tracking Protection. Firefox shows a purple shield instead of a gray shield at the left end of the location/address bar in case Enhanced Tracking Protection is blocking content.

• click the shield icon for more detail and possibly disable the protection

You can check the Web Console for relevant-looking messages like blocked content.

• https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop
• https://support.mozilla.org/en-US/kb/total-cookie-protection-and-website-breakage-faq
• https://support.mozilla.org/en-US/kb/trackers-and-scripts-firefox-blocks-enhanced-track