How did you do the copy? These are recommended steps: You did not explain how you copied. If you used thunderbird's zip export, it REMOVES passwords. A better approach might be this:

Here is the link for moving a profile in Windows when installed in default location:

https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer

here is the info in brief steps:

1. ensure thunderbird is NOT running on old machine
2. enter %appdata% in search window on task bar and press Enter key
3. this should open windows file explorer in Appdata\roaming folder
4. highlight the Thunderbird folder and copy to external media
5. ensure thunderbird is installed on second computer and NOT running
6. enter %appdata% in search window on task bar and press Enter key
7. you should be in Appdata\roaming folder , copy&paste the exported Thunderbird folder there. This may prompt to overwrite an existing folder of same name. allow it
8. start thunderbird and all should be there

Hi David, thanks for your contact, my problem is the file is well over the 2Gb limit, just under 6Gb. I think I must delete some of my saved emails to get the size down. it is sugested to save as multiple zip files, thats another problem. 5 or 6 years back I could manage it but at 82 yrs and Long Covid my memory is Very bad, so much is now dificult, TB and F Fox have been my saviurs. Kind regards Chas

My suggested steps will work, regardless of profile size. Do that and let me know how it goes.