Key stuck in ignition of brand new 2009 Hummer, won't come out

remove panel spray with wd 40

Try using a little electrical contact cleaner inside lock cylinder . pins inside are stuck .
https://www.wikihow.com/Fix-an-Ignition-Key-That-Doesn%27t-Turn

Aside from stuck key, you need a schematic to find out why the ignition switch is dead and not receiving power.

either the key is ruined or you need new ignition , have you a spare key ?

when you shut it off were the wheels cranked sideways-sometimes this puts pressure on the locking system and won't let it disengage-try moving the steering wheel back and forth while applying pressure to the key-I hope this helps-cheers Denny

was the key stuck in the ignition before you change the battery? Is it the right key or it a fresh cut key

u need a new key or its the ignition its self if u go to the dealer ship u can buy a new ignition and the key comes with it or u can try a new key but if u buy a key its just as expensive as duying the whole ignition

turn your steering side to side into you can get the key, make sure is in neutral

Hello did you checked the security system for your car Because the new cars have anti-thief system check it with your car company. i am sure it might help. Please rate my comment thanks

Go buy some WD40 and spray it inside the ignition and while your doing that try and move the steering wheel side to side and try pulling out the key. You might want a extra person to help you let then turn the wheel while your pulling on the key but first spray WD40 in there it wont hurt it plus it lubricates the key and ignition trust me this works I have done this tons of times.
PS you can buy WD40 at any auto parts store or even at a Wal-Mart.