Did you delete the msf files. e.g. Inbox.msf, Sent.msf? In any case, an Inbox file of 0 bytes contains no mail. What about the pop.cogeco-2.ca folder? It may be where the most recent mail is for the Cogeco POP account.

How did you transfer the data from W7 to W10?

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

Just a quick thought - if you switched from POP mail to IMAP in 2018, the newer messages could all be on the mail server. In that case, once you re-establish contact they should appear. Check IMAPMail folder for indications of recently used IMAP accounts. sfhowes - back to you! Agnes

sfhowes said

Did you delete the msf files. e.g. Inbox.msf, Sent.msf? In any case, an Inbox file of 0 bytes contains no mail. What about the pop.cogeco-2.ca folder? It may be where the most recent mail is for the Cogeco POP account. How did you transfer the data from W7 to W10? https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer

Yes, I have done the .msf, and did folder repair, no change. I copied the profile and pasted it into TB on W10. When I open TB on W10, mail page comes up, with folder lists, but no mails in the folders. Nothing happens when I try to get mail. Windows working thingy goes. Cogeco-2 shows 0 kb as well.

AgnesRM said

Just a quick thought - if you switched from POP mail to IMAP in 2018, the newer messages could all be on the mail server. In that case, once you re-establish contact they should appear. Check IMAPMail folder for indications of recently used IMAP accounts. sfhowes - back to you! Agnes

Thanks, but I use POP. Checking IMAP mail shows 2018 date as well, and 0 kb.

Copying a profile folder from one computer to another is not as simple as it was before TB 68. Copying the Thunderbird folder is recommended:

Copy the Thunderbird folder on the source to a flash drive:

C:\Users\sourceusername\AppData\Roaming\Thunderbird

Delete the existing Thunderbird folder on the target:

C:\Users\targetusername\AppData\Roaming\Thunderbird

Copy the folder from the flash drive into Roaming:

C:\Users\targetusername\AppData\Roaming

Do all of this with TB closed. AppData is a hidden folder by default. If possible, update the source and target to the same version of TB before the transfer.

If you follow these steps, the W10 setup will work just like the W7 setup.