I have tried to replace thunderbird profiles (on user/library)

Might not be a good idea.

> messages disappeared

That broad description covers a lot of possibilities. Please post a screen shot.

Thank you for your reply. I highly appreciate your concern.

About a week ago I got a message like 'you can upgrade TB now'. I did that, assuming incorrectly that I would be upgraded to 90 something (I forget, the next version of what I had). I had seen announcements of 115, but didn't understand that simply upgrading would not be sufficient. When I then tried to open TB I got a message to re-install one of my accounts. I don't have a screenshot of that, but I am sure you are familiar with it. I filled out the password, etc., but then only got the emails of that account. I couldn't find a way to put in the details for my second account. What I deplore is that I lost all the emails of accounts that TB was able to show that are no longer active. I don't use them frequently, but once in a while I check on addresses. My problem thus is: how to get all the emails back, not only those of my active email addresses, but also those of my former addresses. What happened next is that I checked on the Internet how to solve this problem. Most of the respondents advised to use the recent TB data as filed under Thunderbird in Library in my user account. I was advised to replace the TB folder in Library for the new TB by the older TB data. This did not work. Unfortunately, my daily backup program then deleted the most recent TB data I had. Fortunately, I have other backups with older TB data (dating beck to before the email addresses were terinated. What I hope you might help me with is a) how to get the emails back under addresses that are no longer in use; b) if a) has no answer, I hope you can tell me how to recreate both of my active addresses. I apologise if I come over as inexperienced (stupid?). My hope is that someone with experience can help me get back all emails. Unfortunately, I can't recreate what my TB looked like before (and make a screenshot). I hope my 'story' above is sufficiently informative!

Would it be possible for you to continue to help me? If not, please let me know.