Here are the possible reasons and resolution for these:

1. Reason: SMS service is not activated on the SIM. 

Solution: Please check this with your network operator and enable SMS service. 

2. Reason: You SIMS has been deactivate for some time (you have not sent or received SMS or calls on the SIM for some time). 

Solution: Network operators will deactivate you on the GSM network if you are not generating any traffic to handle more active traffic. You can check this with AT+COPS? on most GSM devices. If the result is +COPS=0, you must register yourself afresh to the network. 

If after trying the above two solutions SMS are still not delivered you can remove the SIM from the device and insert it into your phone. Re provision the device via your account on InstaMsg platform. Once you receive the SMS store it on your SIM. Now remove the SIM from your phone and insert it back into the device.