NOTE: This issue is NOT with the computer I am using at the moment. That computer runs OSX Sierra.. So disregard my "Shared Data" info. For reasons I will rant about below, I had to trash my copy of FF v69.0.1 Mac and restore it from the .dmg file. FF will not allow me to activate the correct profile, only the new empty profile. Maybe because the accidental installation of (several copies of) newer versions changed some of the items within the "old" profile (they have today's date) ??? Do I need to scrub every hidden bit of FF, beyond Trashing visible files (except for the Profile I desire to keep) ? Then re-install v69 so it doesn't tell me I'm installing an old version? Or will the "todays date" data within the Profile screw it up anyway? Copying the Profile file list & getting it to this computer to post here would take a lot of time & effort. But its the files at the top of the Profile's file list, maybe 25% or 1/3 of the files, when ordered by date. '''PROFILES:''' default-release-6 CREATED WHEN OPENING "NEW" INSTALLATION OF v69-0-1 default-est THIS IS THE ONE WITH ALL MY DATA NOTE there were many others, either leftover from very old FF versions or junked Users, and for every accidental newer version installed (see below for how that happens without user permission). I trashed or archived them. '''WITH FIREFOX RUNNING, ABOUT:PROFILES GIVES AN ERROR & WON'T ALLOW ME TO "DEFAULT" the PROFILE ORIGINALLY USED WITH THIS VERSION:''' "you've launched an older version of firefox...can corrupt stuff...that was already saved to an existing profile create new profile OR quit" This means it is impossible to re-install an "old" version of FF unless you want to lose everything in your profile !!!!! I have tried to manually copy & paste the "old" contents into the "new" profile, but I get the same error. Tried with FF closed, but the Terminal keeps telling me there is no such file: /Applications/'''Firefox.app'''/Contents/MacOS/firefox-bin -P AT ONE POINT I TRIED TO MAKE IT MATCH THE FILENAME I CHANGED IT TO (I LIKE TO SEE THE REV IN A FILENAME) - DO I NEED TO PUT UNDERLINES INSTEAD OF BLANK SPACES? /Applications/'''Firefox 69-0-1 re-installed from dmg.app'''/Contents/MacOS/firefox-bin -P SO THAT IS WHEN I TRASHED THAT RENAMED COPY OF FF, -- because OSX SIERRA WILL NOT ALLOW ME TO MOVE IT OUT OF THE APPLICATIONS FOLDER TO ARCHIVE IT (ANOTHER REASON I WANT TO STAY WITH EL CAPITAN MY MY COMPUTER). '''RE location of Profile files:''' about:profile shows TWO paths, what gives with this? The path that you can Show In Finder yields an empty folder. Are they invisible? But the other path, which I think is the one I have used in the path, does have Profile folders within it: CORRECT PATH TO FIREFOX PROFILE FILES: /Users/admin/Library/Application Support/Firefox/Profiles BUT DELETING FROM HERE DOES NOT REMOVE THEM FROM THE ABOUT:PROFILES LIST, EVEN WHEN I CLOSE FF & RE-OPEN IT - wtf ??? The about:profiles link to show it in Finder goes elsewhere & is empty: USERS/ADMIN/LIBRARY/CACHES/FIREFOX/PROFILES ARE THEY SET TO BE INVISIBLE? THIS USER DOES NOT HAVE THE 3rd PARTY APP TO MAKE THEM VISIBLE. '''THE FUNDAMENTAL PROBLEM THAT GOT ME HERE:''' I foolishly decided to give the next rev up a try, v 72-something. But when I opened it, the default of "automatically install updates" did so to v93, without my knowledge. This happened a few times in a row, when I kept wondering why I did not have v72 running & kept re-installing from the v72 dmg file. I was unable to make my v69 profile the default for either v72 or v93, don't know why not. THE AUTO INSTALL SHOULD ONLY GO TO THE NEXT REV, NOT THE MOST RECENT, WITHOUT USER PERMISSION. So I trashed most everything and installed v69 again from the dmg file. When I opened it, I quickly went to Prefs/Gen and un-toggled the Auto Update. It asked me if I wanted to cancel & I did. '''This is only possible because I have a slow DSL line. Anyone with a T1 line would be screwed.''' So I have a "fresh" copy of v69 but I can't put the CORRECT Profile into it !!!