What to do when Telephony Cards are not recognized
Run lspci to check if the OS detects, if the card is not detected, you may want to move the card to another PCI/PCIex slot
Run dahdi_tool to confirm that DAHDI loads the module, if the application does not detect the card, you may need to upgrade the version of DAHDI and make sure that the module files loads all the modules
Check the configuration to confirm it is set up properly or run dahdi_genconf to auto-generate the configuration
Check /etc/asterisk/chan_dahdi.conf for dahdi-channels.conf. If it does not exist, add #include dahdi-channels.conf
After this is done, restart asterisk
NOTE: You may need to comment out all other includes if you run into issues and make sure only chan_dahdi.conf and dahdi-channels.conf are included