Please describe in full detail how you backed up and moved the profile. That may prove helpful.

I did a Thunderbird backup on my original computer. It created the Profile folders. I saved the backed up profiles to my seagate drive. On new computer I downloaded/installed Thunderbird and then restored profile from backup drive. Everything came back as backed up EXCEPT for the Calendar.

was thunderbird running? how, in detail, did you do the backup? did you backup the thunderbird folder, or just the specific profile folder? did you use windows file explorer to do the backup, or did you use another tool for that? how did you restore the profile to thunderbird - with windows file explorer, thunderbird import? other? knowing the details sometimes helps. if the calendar was in the profile, it should have been there.

I backed up everything in Thunderbird mail as per instructions as to how to backup mail (as I recall that meant finding and saving the Profile files but I have done so many things since then....). With my new Thunderbird installation on my new Windows 11 computer, I followed set up instructions and did whatever I was told to do to "import" Profile. It worked...everything came up on my new computer EXCEPT for the calendar data. Brand new empty calendar and no way to import local.sqlite file....

I started from scratch, multiple times...same result. Don't know what else to tell you.