Help with SIM808 GPS/GPRS/GSM Shield For Arduino

I purchased a SIM808 GPS/GPRS/GSM Shield For Arduino and managed to get the libraries installed, and can get my computer to communicate with the board.

I'm using the sample TCP Send Get Requests sketch and the program code gets past the initialization stage however I am receiving an error message Sim808 join network error message. This just keeps repeating. Below is the exact output from the serial port monitor:

AT+CSTT="cmnet","",""
AT+CIICR
AT+CIFSR
Sim808 join network error

I purchased my SIM card through Aeris and managed to figure out how to activate it. This is what the screen looks like:
I've attached two pictures from the Aeris dashboard.

I'm not sure of what to do next. Please help

Thanks,
Keith