Sorry to hear about this bad upgrade experience. As a first step, if you haven't tried it already, could you do a regular shutdown and restart of your Mac to clear up any file locks and complete any deferred upgrade installs? Next, Firefox won't retain settings if it is running from an installer file (DMG) instead of the Applications folder. An update shouldn't break that, but I guess it may be necessary to check. See: [[How to download and install Firefox on Mac]]. (Sorry, as a Windows person, I don't know the intricacies.) Next, to connect Firefox to an older profile, try the Profile Manager Page: Inside Firefox, type or paste '''about:profiles''' in the address bar and press Enter/Return to load it. This page should list at least one profile and could list many. (Each profile has two folders and one or more buttons. Do not use any Remove buttons!) The profile that Firefox is currently using will have this: '''This is the profile in use and it cannot be deleted.''' For any other profile you find, check whether it is the one you were using recently by clicking its '''Launch profile in new browser''' button. If it isn't what you want, simply close that new window. If it IS what you want, back on the about:profiles page, click the '''Set as default profile''' button for that profile so Firefox uses it automatically at the next startup. Any progress so far?