My screen cracekd a few weeks ago, so I ordered a new replacement screen. Arrived and I replaced it, I put most of it back together bar the back cover and turned it on to test everything was working. Everything worked so i turned it off again and started putting it back together. Once I tried to turn it on again the screen never came on. I can here the noises of the charger disconnecting and reconnecting. Can hear messages being received but the screen is not turning on. Any one any ideas what has went wrong and if it is fixable?