Do you have something like the following:
voice grouped-trunk PRI
!Replace the XXX-XXX-XXXX with a proper call pattern for the trunk
accept XXX-XXX-XXXX cost 0
Thanks for the email.
The issue was with the old firmware we had on the system which evidently has some bug with the channels not getting assigned even after the configuration is complete.
We had to drop the isdn from voice pri and upgrade the OS and then re-add the isdn 1, to get it working