I own a 2019 GMC Sierra 500 AT4 and I have been having the same issues with starting my truck and or it does not read the Fob.
Took the truck into dealership and of course nothing found.
This last time my cousin started the truck while I was gone and in week two I started the truck with my Phone app.
Got home on week three and it was completely dead. Took the jumper cables and a jumper box to start the truck. Prior to that on the screen I did not have the GMC emblem I had the Cadillac emblem.
Dealership said it had some faults and claimed the batter was fine until the day after returning from surgery, one day and the truck had to be jump started again. May be time to trade this truck in.
I hope this helps others and someone may have suggestions.