Unable to play YouTube videos

I'm having an issue playing YouTube videos in Safari. Whenever I open a page I'm asked to sign in and refuse which causes a playback error in the video. In private browsing refusing to sign in prompts a new box to appear asking for me to agree to their terms of service. After agreeing videos play without issue.

Clearly the playback error is occurring because I haven't agreed to the YouTube terms of service, but I can't agree to them because the prompt doesn't appear. I saw some posts from a couple of years ago saying that Safari had some issues with Javascript handling, I'm assuming those have been fixed but could this issue be caused by something similar? Has anyone had similar issues, or have any ideas about how to fix this?

I'm on a late 2014 Mac mini (Macmini 7,1) running Big Sur 11.2.3 and using Safari 14.0.3 (16610.4.3.1.7)

Cheers