Either the digitizer connector isn't properly connected or you need to clean the connectors on the maimboard with some alcohol. If this doesn't work then your screen is faulty, get it replaced by the seller. Ive had this more than once happen to me and its usually a faulty screen.
Either your new screen is faulty or you damaged the flex cables. This is definately a screen problem. Switch it on with the screen separated from the case a little bit so you can take a look inside to see if the backlight is turning on, it probably isn't