your keyboard is dead, time to get a new phone, go through insurance if u have it, mine just died last week the same way, i tested it by flashing a few roms and even the stock one and nothing, itll light up but fade out but nothing happens when i mash all the buttons, dead keyboard. it would sporadically work once and while but almost 98% of the time it wouldnt so i already got my new refurb from sprint on thursday, if u have sprint,
go here to get a free replacement (if u have tep). and u should get one via fedex by tuesday, or else goto a repair shop and maybe they can fix it