New PK III key made and still wont start

Something with the anti theft system is screwed up more than likely your car doesn't have a chip in the key. The transponder or exciter in ignition switch can be screwed up or maybe a connection problem.

This car uses the Passkey III system that does have a transponder in the key.

You should be able to do a relearn yourself though.

30-MINUTE RELEARN PROCEDURE
Use this procedure after replacing the following components:

The passkey III (PK3) keys
The theft deterrent control module
The PCM, see important above

IMPORTANT: This procedure is not available on vehicles equipped with option code (Z49 or BAE).
If replacing a theft deterrent control module with an GM SPO Replacement Part, perform the procedure to setup a new theft deterrent control module prior to the 30-minute relearn procedure.

With a master passkey III key (Black), turn ON the ignition, with the engine OFF.
Observe the Security telltale, after approximately 10 minutes the telltale will turn off.
Turn OFF the ignition, and wait 5 seconds.
Repeat steps 1?3 two more times for a total of 3 cycles or 30 minutes.

IMPORTANT: The vehicle learns the key transponder information and/or passwords on the ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.

With a master passkey III key, start the vehicle. The vehicle has now learned the key transponder information and the PCM has now learned the fuel continue password.
With a scan tool, clear any DTCs.