Yo how did you solve initial problem? Im having same issue. Works when i upload empty sketch but then when i upload the parsing sketch change sketch to 8,7 and everything i just get question marks on the serial monster. I believe the issue is that my gps isn't finding a fix but I waited like 45mins and then just gave up. How did you fix yours. For anyone else that has questions for me Im following the steps for the gps logger shield on the adafruit website