Dahdi vs zap device issue

New install, FreePBX on Asterisk, Centos 5.6. I have a 24 port Digium AEX 2400 analog card, and when I create a ZAP device, it works, the extension can make and receive calls (although *65 comes up blank on the device, so something is wrong in the database somewhere). If I try to create a Dahdi device, the “channel” dropdown is empty; it seems not to be recognizing the analog card.
Amportal.conf is set to “device and user” because we do hotdesking. Any thoughts appreciated on how I can get the dahdi module working, thanks.