I had same error. I solved it this way:
cd /usr/src/dahdi-linux-2.11.1/
make (Verificar there are no errors)
make install
/etc/init.d/dahdi start
dahdi_cfg -vv
It shows:
DAHDI Tools Version - 2.11.1
DAHDI Version: 2.11.1
Echo Canceller(s):
Configuration
Channel map:
0 channels to configure.
Next:
amportal restart
Now it should work conference and paging