Why won't my phone come on?

A

AC Question

Why wont my phone come on

My husband has a galaxy note 2. Last night he said he had a update from at&t and after he updated it it wouldn't come back on. its just a blank black screen.. ive tried turning it on ive also tried holding the power button home key and volume up key when I did that the screen came on and updated when it got to 100% it said galaxy note2 like it normally does when its coming on then it went black again.. its shown the battery in green when I had it plugged up showing it had 50% charge so I know its not dead... any ideas on what it could be or what to do? it worked fine before the update... Thank you