Thank you! @ Dropa

Try a better content blocker, such as the following.

https://addons.mozilla.org/firefox/addon/ublock-origin/

mozilla sent me a new Firefox ios and i installed it on new imac. No adblocker extensions are installed. Still can't browse YouTube now. I still can on my old macbook pro firefox, same account.

You can create a new profile as a quick test to see if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles

If the new profile works, you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

Not a very good solution, however, after digging around I've found that Brave "out of the box" works fine on YT. This tells me that is can be done, however, Firefox isn't doing it.

Another work around I've found is to log out of your Google account then open YT without an account.

Basically, we get to wait for FF to fix this or move to another browser.

Google often runs experiments so you should expect to see different results based on your cookies, login, IP address, browser and other factors.