Please explain the problem in detail. What happens? What is/are the exact error message(s) ?

Auto filling what?

When you have a blank box asking for an Email address, or Name, or address, password, etc...When you click on it...it used to fill in automatically...Now it does "Nothing" (NO ERROR Message) You have to fill it in yourself. Funny thing is it still works OK with Chrome and I really do not want to go back to using that! When you go into Settings and select sync and everything is checked and Saved....It still does nothing. Firefox 95.0.2 64bit Windows 10 pro. This just stopped working recently and the only thing I can think was added was Norton 360 but I have used Norton antivirus in the past and never had an issue, plus any windows updates. Really irritating!

Sync is used to share data between different Firefox profiles and systems.

What you are talking about is the Form Filler built into the browser.

https://support.mozilla.org/en-US/kb/automatically-fill-address-and-credit-cards

https://support.mozilla.org/en-US/kb/control-whether-firefox-automatically-fills-forms