I have seen this error many times on iphones with broken baseband chip after water damage or impact damages.
Itunes trying to read device's baseband chip (IMEI number or something like that) to activate the phone.
I guess same thing happening to your ipad CDMA. Baseband chip looks like not functioning.
Reasons
1- If its water damaged try to clean mainboard shortcuts and resolder corroded components.
2- if it has impact damaged, using hot air on the baseband chip may bring the baseband function back. I dont know What temperature and howmany minutes. But you can google for it.
Good luck ...