I lost the key & transmitter for my 2004 Envoy. Had a new key made at the GMC dealer. Worked great one time. Tried later and it seems the alarm set itself. Cannot get the alarm to disengage thus letting me crank the car. I have many things no luck. Advice?

Ignition keys relearn takes about 30 min to do. 30-Minute Learn Procedure 1. Turn ON the ignition, with the engine OFF. 2. Attempt to start the engine, then release the key to ON; the vehicle will not start. 3. Observe the SECURITY tell tale light. After approximately 10 minutes, the light will turn OFF. 4. Turn OFF the ignition switch, and wait 5 seconds. 5. Repeat steps 1 through 4 - two more times - for a total of 3 cycles of 10 minutes. 3x10 = 30 minutes. The vehicle is now ready to relearn the Passlock Sensor Data Code and/or passwords on the next ignition switch turn from OFF to CRANK Important: Turn the Ignition Switch OFF. The vehicle learns the Passlock Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle. 6. Start the engine. The vehicle has now learned the Passlock Sensor Data Code and/or password. 7. With a scan tool, clear any DTCs if needed. History DTCs will self clear after 100 ignition cycles. Without a scan tool you may have momentary starter interruptions while history clears itself.