My 2000 Ford Ranger won't start and theft light flashes

My 2000 Ford Ranger won't start and theft light flashes My son recently pulled our 2000 Ford Ranger XLT from northern Utah to Louisiana on a dolly. it was very cold, rainy and snowy otherwise non eventful. On arrival he tried to start the vehicle to back it off the dolly. The theft light on the dash flashes and the engine turns over but it will not start.