GPS example on GrovePi


i am a new user of raspberry GrovePi, and i try to use a GPS!
My problem is that my example didn’t work :’( !
i tryed to use the example for GrovePi here

it return “Unable to read” and the error is in the vals method , lat_ns=GPS.GGA[2] is out of rang.

someone can help me please :’( !?