I have a iphone 5s that will not power on, itunes will not respond to it. I have changed the battery and it seems to be getting proper voltage. The screen will not turn on, it makes no sounds. It seems to respond to nothing. I have tried to put it in dfu mode with no response. I have tried holding the home/power button at the same time with no response. I have tried to connect it to power without a battery with no response. It is not water damaged. I need help on what steps i may need to take next. Thank you!