Hey there, If eBay login suddenly fails on Firefox with the message 'Oops, that’s not a match,' start by clearing your browser’s cache and cookies, as saved data can sometimes interfere. Next, try disabling extensions, as ad blockers or privacy add-ons can block login functionality. You can also test logging in from a Private Window to see if it’s an issue with cached data or extensions. Finally, ensure Firefox is updated and, if needed, refresh Firefox settings to reset any problematic configurations. Mike Taku.