Major Steve

Hi, everyone looks like you have a great forum here. I have a 2016 Chevy 2500 hd lt with power door locks and no remote entry system it does have the tire pressure sensor system. I purchased a Doorman key fob and programmer. With key in run position plugged the programmer it beeped, the "remote key learning activate" came up in the information center, I pressed both lock buttons for over 30 seconds and nothing happened. Called Chevy to have them sell me a fob and program it. They said they had never done it and would try it but if it didn't I would still have to pay for their effort. Any ideas? Thank you