SIM7000E - Failed to attach GPRS

Hi I'm using your SIM7000E expansion shield with an Arduino Uno, and Arduino IDE v1.87. I'm running into an issue where I'm running the sample code you provided and it continuously fails to attach the GPRS service. Could somebody please help me fix this? Also, could somebody please advise whether a GRPS connection is necessary for NB-IoT usage? I'm supplying 9V to the Vin pin so the device is fully powered.