my iphone 6 turns on with old screen it was cracked so replaced it and also replaced the battery to be sure . I put the old screen back on and tried to hard restart and the screen came on and showed the download screen. so i turned it off and put the new screen back on and when i got the connections on i turned it on and the screen turned on so shut it off again and finished putting it back together and now it won't turn on again even trying to hard start it again I hear it on itunes but it shows nothing