O.k.,what may have occurred here as I have seen in the past is the BCM (body control module) may have become wet and damaged internally.When this occurs it will cause these symptoms here and usually needs replaced to correct it.This BCM is located under the dash/center console to the passenger side of the dash and shifter assembly.In some cases it may dry out and operate again and in others I have had to replace it.
If it doesn't operate after allowing the vehicle to sit and dry I suspect it would need replaced.When it is replaced the new one would need set up and programmed by a dealer with their scan tool and GM computer in order to operate properly.
There is a security relearn you can try and see if it operates or starts then.If it does the dealer would still need to recalibrate the radio to get it to operate as well using their computer and scan tool.Here is the relearn you can try,make sure you follow it exactly with a fully charged battery.If you miss a step you wold need to start over.If this does not work most likely the BCM would need replaced:
1. With your key, turn ON the ignition, with the engine
2. Observe the security indicator. After approximately 10 minutes, the telltale will turn OFF.
3. Turn OFF the ignition, and wait 5 seconds.
4. Repeat steps 1-3 two more times for a total of 3 cycles or 30 minutes.
5. With your key, start the vehicle.If this worked the vehicle should now start and run.
is my profile if you need anything in the future on your vehicle here,you can save it to your favorites and come back if you have any future questions on your vehicle (besides this question here).