Hello tom164, The problem you have seems to be a bug. Report the bug here, https://bugzilla.mozilla.org/home. Please tell me how it goes and , Stay Safe!!

goes again, have deleted the entire Chronic including temporary files.

the problem keeps reappearing

That's interesting, maybe try clearing your cache? Ctrl+Shift+Delete and then on the top, select everything (NOTE: this will delete all your browsing data). Tell me how it goes!

PS. Sorry I didn't respond earlier, I thought you got it solved

i think i found the problem.

if i access the following page (https://downloadcenter.intel.com/de), then click, left, on the "X" at the bottom of the message "Cookies on this page", then go to the page described above, and the side will be displayed empty.

than clearing the cache and the page is going.

when i access again the page (https://downloadcenter.intel.com/de), then click again, left, on the "X" at the bottom of the message "Cookies on this page", the same problem again.

this problem doesn´t exist with Firefox 75 und earlier

Correct! That's great! If you don't want to happen in a long time, try clearing the cache of a longer time. To clear cache: Press Ctrl, Shift, and Delete at the same time.

As again, tell me how it goes and,

Stay Safe!

However, the problem still persists, i.e. as soon as you go to this Intel driver page and confirm or click away the message regarding cookies with "X", the Intel Community page will no longer work. Only again when you clear the cache. If you go back to this Intel driver page and want to go to the Intel Community page later, you always have to clear the cache beforehand. And since that wasn't the case before, I assume it's a mistake.

Hmm... That's interesting. I'll try to research a little bit more but I think you should wait for someone who knows more than I do to help you out. Thanks!

I have reported the whole thing on bugzilla as you suggested.