Remote will not open the car
Remote battery dead? If not then something has happened to either the remote or the receiver in the vehicle. If it is still under warranty take it in.
It may have to be reprogramed. Was the papery disconnected or was it jumps started? The computer is a finicky thing. But do check the battery first. The GMC came with two remotes. Did you check the other one? Fuse? Alarm system? Does the rear deck lid function? How about the remote start? Alarm work? If nothing works, it is a fuse, battery, remote, or $$$$.
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