ok dome lights for denali

Ok I just bout an 05 yukon Denali, basically stock except for an alarm and amp wired up. Well on the first night I noticed none of the dome lights were working except for the exterior lights and drivers door entry light. I checked the bulbs in the dome lights no they were fine, checked the switch and that worked y illuminating the drivers door, dome over ride works but only on that door as well. ( Ill check the passenger door light bulb tomorrow ) So I figured the alarm must have turned off the dome lights, so I took it to the cartoys where it was installed and they said they didn't do that, and can't. The install guy looked at it real quick and said its not the alarm. What else could it be?

Check the wiring at each position, either two wires 12V+ and switched ground via the door opening or the above two and a constant ground. Is there a sleep timer on this vehicle? Shuts these lights off after 10 minutes or so if a door is left open?

Yea there's a sleep timer I guess since it does turn the lights off after a few seconds (adjustable time in the vehicle computer via dic) I know there was an alarm with remote start before, and then it was replaced with just an alarm at cartoys, assuming there was some problem with the first alarm. (Cartoys folks told me that because there were notes in their system)

Possibly faulty timer.