Check to make sure all your spans are enabled in the /etc/zaptel.conf, if not correct the error and reload the module module. A complete example to fix the problem is as follows:

span=1,0,0,esf,b8zs
span=2,0,0,esf,b8zs
span=3,0,0,esf,b8zs
span=4,0,0,esf,b8zs