I don't know if it will be helpful in your situation, but I found Refresh Firefox - reset add-ons and settings | Firefox Help.

Although it may not help, it sounds like it can't hurt other than by costing you your Add-ons and possibly some settings. (You may want to back up ~/Library/Application Support/Firefox/Profiles first.)

More: Maybe run it on Firefox v 66 and then try to update again?

Last edited by artie505; 06/22/19 03:56 PM. Reason: More
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