SIM808 GPS/GPRS/GSM arduino shield not working

As part of my Final Year Project I am using the SIM808 GPS/GPRS/GSM arduino shield to use the GPS and GSM features. I am having a problem where when I press the boot button on the shield the Net LED flashes as normal until the GPS is successfully turned on then the Net LED stops flashing and no further data is retrieved and nothing is printed on the Serial Monitor.
I thought this could be a power issue but I have recently brought a new battery and the issue persists. I have also purchased a new SIM808 GPS/GPRS/GSM arduino shield and the problem still remains. I am using the same code that worked before the issue started.
PLEASE HELP
Thank you in advance.
For SIM808 GPS/GPRS/GSM arduino shield(SKU:TEL0097), the GPS function will only work if you set yhe GPS antenna outside before it can obtain a stable GPS location data output.
Also, could you please try AT command? See whether the module work properly.

For more details see the WIKI page here.
https://wiki.dfrobot.com/SIM808_GPS_GPRS_GSM_Shield_SKU__TEL0097
