I had a similar problem on a trip to Texas. Onstar did their diagnostic thing and said they would have to get me a wrecker.
So, we rode in the cab of a car hauler to a Cadillac dealer in the city of our destination. We arrived at 1:30 AM.
The next morning I called the dealer and the service writer said my ignition was not talking to my security system, and they would put in a new ignition switch. I picked up my baby that afternoon. No problem since.