"This profile was last used with a newer version of this application. Please create a new profile."

Firefox tech explanation is whattrainisitnow.com that lists different release channels for different use–cases, systems and/or audiences. Firefox user explanation is [[Choose a Firefox update channel]] and [[Firefox ESR release cycle]] — the currently outgoing 140esr will be replaced with already available 153esr in a few weeks anyway. Your profile data from recent 156 release won't be compatible with either of the two slower branches (IIRC there were password encryption changes around v148 and v155, so going "backwards" even manually will mean passwords will get lost — the profile compatibility lock and protection is in place exactly for this purpose, to avoid any potential data loss). I'd advise against similar downgrades, and if you need to test older versions on the side, to do that in isolation (I can share some links later). The fix here is to download regular release from firefox.com and installing this current version over what you have — which should unblock your using the profile as a first step now. (Or, if you don't have any stored passwords, you don't use sync with other devices etc., and want to try the forced downgrade after all, there are also some options that might yield some results if you're so inclined.)