TPMS wont program to my truck

[327chevy]

I had a factory sensor quit working so I bought an aftermarket one from my local auto parts store,for get the brand.Anyway went to my mechanic and he said no big deal,pop it in and program it to the truck and done.After 4 days of messing with it he admitted defeat.He could not get my truck to accept the new TPMS that I bought or another brand one he picked up to try.He told me that another customer with a GM truck was in his shop so he tried paring the sensor to it and was successful but for whatever reason 2 new TPMS sensors would not pair to my truck.I have 4 winter tires and rims with GM sensors in them and I'm going to swap one of those into my aluminum wheels for now but I'd still like to know if anyone else has run across issues with pairing and aftermarket TPMS with their truck. I have an '08 Silverado crew cab w/5.3 litre in it and the only alteration I've done electronically would be the addition of a Pioneer dvd head unit and a backup camera.