405. That’s an error.

Firefox updated to 82.0.3 (64-bit) Cookies cleared. Signed into YouTube. When I'm in YouTube and want to mark a video watched I click the 3 dots and select "Not interested". When I then select "Tell us why" the pop up to select "I've already watched the video" does not appear. In some instances "Not interested" does not appear but only "Add to queue". Further, my subscriptions are not displayed. Instead there it says, "Sign in to like videos, comment, and subscribe." with a sign in icon. This is weird as I am signed in according to the icon in the upper right corner. If I click the icon a page loads (https://www.youtube.com/youtubei/v1/guide?key=AIzaSyAO_FJ2SlqU8Q4STEHLGCilw_Y9_11qcW8) with the following message: 405. That’s an error. The request method GET is inappropriate for the URL /youtubei/v1/guide. That’s all we know. None of these issues occurred prior to updating Firefox nor do they occur in Chrome.