Hi,
you need to go to the "fop2 buttons" menu in freepbx/fop2admin and add your dahdi channel ranges, like 1-24 or whatever ranges you might have for your DAHDI trunks.
Also, if using a dated fop2 version you might need to add one line to the autoconfig-buttons-freepbx.sh script. It was discussed many times in this forum already: View Post 1243
