The following links might be helpful:

1. Upgrading from an older version of Thunderbird https://support.mozilla.org/en-US/kb/upgrading-older-version-thunderbird

Quotation from the above link:

Important: Before upgrading, always back up your profile.

2. 141 Update - Killed Filtaquilla https://support.mozilla.org/en-US/questions/1524575#answer-1751064

Quotation from the above link:

The above add-on ("Add-on Compatibility Check") can check whether installed add-ons are compatible with new version of Thunderbird. Therefore, you can decide whether to upgrade Thunderbird or not.

For some reason I couldn't update from 115.10.1; I don't recall but I think it was showing "You're up to date" --- for months. When I went to post a question, I got an account not active error. When I received a confirmation code to verify the email address and activate my account, there was no place to enter the code. Eventually I got my account activated, posted my question. but none of the suggestions from support worked. I checked for updates periodically with no success; but after 2 days when I checked I was presented with update to 128.13.0esr. After that update; I checked the Help menu again and was presented with update to 140.1.0esr, and I updated. My account not being active may have been why new updates weren't shown; but I don't know, I never had a problem updating before even though my account was apparently inactive; maybe esr requires an active account.

Hello there

These updates can or did came automatically on screen if automatic updates where involved, that process is normal , if they do appear onscreen.

First you can try to update to Thunderbird version 115,0. Then other update messages can appear to update to , yes and from there on it can become that update s can appear onscreen and from there on to go to version 140.1 esr.

Yes, updates can be blocked for the program if other issues are involved in that situation there , common blocks that can be involved there are  :

Account is not active or deleted at that time of updates. If problems did occur in the server system it can be that it is blocking that update process. Recent antivirus programs or firewall s can block these updates try to lighten up the scans. Also the Profile could be damaged somehow and somewhere and updates cannot be updated then temporarily. Or that server system is temporarily out of function and cannot be active for that account that has to be updated then and that could be the curlprit there. You can or could had reached out to update the software manually if other things did not work together there then , and that had be worked for that situation to go and to do for that proceeding to get these newer update s and going to newer versions there.

It might be that these messages that came up onscreen and went not from thunderbird itself but from the pc system itself to message you for notification how the system went running at that moment of being active there at that time.

A screenshot could have had something of value for us to peruse. https://support.mozilla.org/en-US/kb/how-to-make-screenshots

Greetings googlethunderbird.

Hello there

If that send code/password is not been asked when it had should’ve be there you can trigger that function by clearing the passwords in the Thunderbird settings. If It seems to having issues with the saving and authentication of password's. Try clearing existing passwords for that subject and restart Thunderbird to trigger that to be prompted for passwords again.

If there are some message s showing on screen , then you can send it to us. So we can look further into that. It might be that you could use some new passwords.

If you like to download that normal version of 140.0 thunderbird . You can do that instead of installing the more stable version 140.esr.

https://www.thunderbird.net/en-US/thunderbird/releases/ https://support.mozilla.org/en-US/kb/installing-thunderbird-windows]

Did you use the inbuilt updater?

Greetings googlethunderbird

Hello there

To download manually try to download version 128.0 of Thunderbird. And climb up to other versions if you want to have that smooth installing and working options of Thunderbird. Updating direct from 128.0 to 140.0 version is possible but the most users are experiencing some quirks then.

Clean the system make some backups of all files yes you need to have backup s. Then start to install all these Thunderbird versions.

You think there might be a way to copy all files and profile map into Thunderbird newer version but a lot of things has to be similar and both version s has to be up to date to sync these backups files and profile map into that newer version , if it ain’t that then new issues do appear with importing them.

Questions are open.

Greetings googlethunderbird.