New Key / Car Doesn't Work / Theft Light

Hello,

I recently lost my key to my Dodge Caravan 2003.

I had to tow the car to the Dodge dealership.

They cut 2 new keys and weren't able to program them as they said my car
was too old for their program after trying for about 1 hour.

They sent me to another guy to program the key and he did it.

Seemed like everything was well until the theft light started lighting on the
dashboard and now the car won't start anymore. It did start on and off for a
day or two now not at all and theft light keeps coming on. We are pretty sure
something happened when they programmed the key but they won't take any
responsibility for it. It was a super expensive thing for us to do that as well :
500 $.

Help please, any idea what could be happening...