Do you have any versions of abook.mab and history.mab, in old profiles or backups? They can be imported in 91 from Tools/Import...Address Books...Mork database...select a mab file.

Hello, After Thunderbird update from 68.9.0 to 91.0.3 my address book was missing. I've already checked abook.mab.bak and history.mab.bak but they are missing too.

Thunderbird's internal update process should be updating first to version 78, and from there to version 91.

Did you use some other process to update?

Hello Wayne. May I post a related experience here?

I also upgraded, probably from v.52.7.0 (64-bit) -- I don't remember -- to v.91.5.1 (64-bit) and lost the address book.

abook.mab (23.4 KB) & history.mab (2.4 KB) both existed. Neither abook.mab.bak or history.mab.bak existed.

Is there a "Thunderbird's internal update process"?

I run TBird in Linux Mint inside a VBox, virtual machine. The TBird application is installed on a virtual USB mounted here: /media/mark/TBird Linux.

My profile is in a shared folder. In the Win10 Host, my profile is here: c:\email\0ysydkep.default. In the Linux MInt Guest, my profile is here: /media/sf_email/0ysydkep.default.

When I update TBird, I simply copy the contents of the distributable (in this case, thunderbird-91.5.1.tar.bz2) to /media/mark/TBird Linux, overwriting all existing content.

I've reverted back to v.52.7.0 (64-bit).

Regards, Mark Filipak.

Indeed, if you don't follow the naturally provide migration path through version 78, then your address book won't be automatically migrated. But there is tools > import > address book > mork