The are both CDMA networks, so that wouldn't be the issue. However if the new phone is locked, then that could cause it. You would have to get it unlocked by the carrier/service provider that it is through.
Also, it is possible that the SIM you are trying to place in the new device is not the right kind for that device. You would have to check with the SIM's carrier/service provider to see if that is the problem, and if so, get them to give you a compatible SIM.