dahdi_genconf creates two files.
system.conf is read by dahdi_cfg which should be called when the system loads the dahdi driver. In Centos that should be the script /etc/init.d/dahdi.
The Asterisk dahdi channel driver (chan_dahdi.so) reads a config file of /etc/asterisk/chan_dahdi.cfg. Under FreePBX, that file ‘includes’ the file chan_dahdi_additional.conf. One of those two files probably ‘includes’ the dahdi-channels.conf file, I do not remember which one.
There is another file that is used when loading the dahdi kernel module, it is /etc/dahdi/modules which lists which kernel modules to load based on the card(s) that are installed in the system. If you are unsure, you can let it load all modules. This file is NOT modified by dahdi_genconf.
If the driver is infact being loaded at system boot, yet the channels are not being configured, you can try adding the command ‘dahdi_cfg’ to the /etc/rc.local script file before the call to ‘amportal start’