MyGMC App

I'm having problems with the MyGMC App for Android. I used it once and now it keeps asking me to login and add a vehicle. I type in Vin, year, make and model it then tells me the Vin is not linked and to link it. Once I hit button to link it gives me an error about the Vin and to try again later then kicks Mr back to the type in Vin screen. Not exactly wanting me to pay for something that doesn't work.