Perhaps next time include some details that someone might be able to help you with. Certainly stating in advance your intention to abandon the software as you did last time is not going to encourage anyone to invest their time in you. I have been responding to basically the same statement since [https://www.thunderbird.net/en-US/thunderbird/68.0/releasenotes/ V68 was released] in 2019. I got so sick of it back then that I wrote a blog post about it. https://thunderbirdtweaks.blogspot.com/2019/09/i-lost-my-profilemail-on-update-to.html This forum is chock a block full of folk with essentially the same issue and getting essentially the same responses. Even in this topic there is this link listed under See also. https://support.mozilla.org/en-US/kb/unable-launch-older-version-profile So why did you not get a reply. I don't know. Will you ever have the same issue again? Probably, those that downgrade to fix the issue and continue to use the original profile appear more prone to the profile per install messing up. Others appear to draw the issue from their system configuration. For me it occurred once, I forced the use of my old profile and everything was good and has stayed good. That is about all I can tell you.