this is a feature, on A/T cars. for vast years, !!!
my jeep is M/T and has no such thing, but A/T has this.
This feature, prevents starting in GEAR.
called park lock out, so the Audi lady can't drive over her kids, ( really sad huh?)
Called BTSI: by jeep.
this feature does, not stop starts/crankikng. unless, the shifter is not placed
in park or neutral. (this feature blocks cranking in any gear)
so i must guess, its in park, engine is running, right?
and your foot, is on the brake, and the brake lights do glow behind car, if not the park lock will stay locked.
if you need a schematic, i can send it.
some cars there is a park lock out bypass so you can drive
with no brake lights. (LOL)
the BTSI bypass is missing this feature, in 2006, unlike older cars.
a federal mandate that bypass removal.
check the brake light fuses first of brake lights are dead.
the post back for schematic.
the FSM covers how to fix this on all cars made, (usa car, and forum)
The OEM "factory service manual" buy one and end guessing.
or login to alldata.com
so does the starter work or not in park or neutral.
this i can not guess from your post. at all.
fails to stay running, engine.
if the key will not crank the engine in park , then try cranking
in Neutral,(this trick uses fresh PRNDL contacts)
if the engine will not crank use jumper cable ump starts from a running donor car, (read paper sheet in cable box, it tells how )
if the car now cranks and starts jumped,that means the battery
was (is) discharged, that can be caused by phantom drains.
all tests are easy, and all take only a 10$ walfart DMM meter.
to find true cause , ask.
try posting what step fails in the operator guide , how to start your engine.
shift to park.
foot on brake,
turn key to crank, does this fail?