SpamAssassin isn't updating the database

==== Required information ====
- iRedMail version: 0.8.7
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Linux/BSD distribution name and version: Ubuntu 12.04 LTS
====

I configured SpamAssassin and it seems to be working well (I'm seeing the spam tagged correctly and it's being moved to the Junk folder as expected). But, for some reason, the sa_bayes database isn' t being updated at all! I've verified that my username and password are correct (when I did the sa-learn command to learn spam, it did it with no problem).

Any ideas what might be going on?

Thanks!