Upgrading 3.6.3 to 3.9.3: no user accounts

I have a 3.6.3 OpenFire server running on a PostgreSQL database. I have setup a new deployment of OpenFire, latest version 3.9.3

When the new server is started and pointed at the database for 3.6.3, there are no user accounts. I can create new users with 3.9.3, but if I start 3.6.3, it won't see the new users either. It's like the two account databases are completely separate.

I didn't see any notable error messages in the logs, including debug. I also do not see indication that some kind of database upgrade was attempted.

Any suggestions on what might be happening?

Cheers,

TTimo