2008 suburban LTZ will not start

[ejstave]

I have a 2008 suburban ltz. It has been in my garage for a couple days and now the key fobs, dome lights, backup lights etc. are not working. When I put the key in the ignition, it will not crank. There is not a security light that stays on or flashes... I also cannot open the rear hatch, or wind down the windows. Very strange. Any idea what it could be?

[ejstave]

I grabbed another battery and swapped it out. No change. both have been load tested and still nothing.