Installing new TB in computer that had old version.

Please clarify what you men by refusing to let you sign in. I am unsure of the problem. thank you

Using a pc. I had to reset windows. After that I downloaded TB and when I set it up, there was no way for me to retrieve the data from the previous version. Previously if I removed TB, the retrieval was easy. Not so now. Does this clarify?

Does Thunderbird on startup display an error message, and if this is the case which is the texte of this message? Does it refuse your password? Or does it prompt to set up your existing email address? Do you remember the "old version" number?

If by 'reset' you mean a fresh reinstall of windows, that would have removed all files from the computer. Other than that, when thunderbird is removed, the profile remains. Then, if a fresh version is installed, it immediately connects with the profile. From what you shared, my inference is that the profile no longer exists.

I have carbonite and it shows a long list of profiles. Is there one in particular I should be looking for?

Look for a file named profiles.ini in the thunderbird folder. That simple text file has the name of the active profile.

The simple approach is to save the entire appdata\roaming\thunderbird folder from the backup and replace the default thunderbird folder after installing new thunderbird, shutting it down.

To clarify: - install thunderbird - delete the appdata\roaming\thunderbird folder - replace with your backup - restart thunderbird