[repairman54]

A full code scan of all 4 code families would be step one to see if any CAN system codes are present. CAN is the onboard computer network. Will not show up in a P code scan tool.
If no codes then maybe a bad keypad in the remote or an issue in the interior switch if yours has one. My '16 does.
Might even be a internal issue in the latch since putting it in gear auto locks the doors.
Just tossing out some possibilities.

 

[repairman54]

There are 4 code families, P , U , C and B.
A scan tool that can read all 4 is a must for one to properly diagnose today's GM vehicles. Some scan tools will only read ABS or SRS but not all 4 so research is involved to get one that is complete for the money.
A popular one is a BlueDriver that is smart phone based. I use laptop based AutoEnginuity program myself.