Problems with a refurbished PCM?

I was having some sporadic no start conditions, so I had the car towed to a Chevrolet dealership. They diagnosed the problem as the PCM being faulty. I ordered a programmed PCM from flagship one and I can't get the key relearn to work with this PCM. For some reason the security light does not turn on at all. I do get a message that says "service theft deterrent system". The car won't crank at all with the new PCM. I have tried this process about 4 times now, with the last time leaving the battery unplugged for about 4 hours to make sure that wasn't an issue. The car will still crank and start with the old PCM. I'm not sure if I'm overlooking something or if the refurbished PCM is somehow faulty.