SB6121 Modem Won't assign IP

Trying to get internet setup at my mom's house.  She just relocated to AZ.

Tech left her house and said internet was good.  I come over to try and setup her wifi etc.

Cannot get the modem to assign router an IP address for anything.

Finally I give up and try connecting laptop directly to modem.  After numerous reboots of the laptop and modem and tryign a different laptop I gave up... 

I noticed that very momentarily when you reboot the modem it would assign an IP to the router. But it would assign it an internal IP of 192.168.100.10 instead of a public internet IP address.  Within a few seconds though it would drop the address and the router would have nothing.

 All the while the modem has all lights connected and shows it's on the "internet"

Found people talking of similar issues with comcast:

http://forums.comcast.com/t5/Basic-Internet-Connectivity-And/Motorola-SB6121-and-unidentified-network-Not-getting-Public-IP/td-p/1953955

Any ideas here?? Guess need to get tech back out here.  Even though modem says "online" I dont think it's fully configured right.