Usually either the key is defective (worn out) or the ignition switch is worn out (which wont recognize the key). Either way it's difficult to troubleshoot with out the GM computer. You could easily spend hundreds of dollars and actually save money by taking it to the dealer. They should have the appropriate tech to fix it.
If this happens, that means the vehicle is not drivable. You should have vehicle towed to a Chevy dealership. They will be able to diagnose the problem where the key is not able to make the vehicle start.
You might be able to replace the transceiver and reprogram your keys yourself but it may not work. Most people need to have a dealer fix this problem for them.
