our touch screen will not boot the image on the sd card, we've loaded raspiban onto it but haven't been able to get anything to display on the actual touch screen. we've confirmed that the unit itself is operational and is able to read the sd card, this was done by connecting the pi via hdmi to an external monitor. the screen powers on and greets us with a blank white screen. I'm not certain whether this has to do with the coding on the sd card or if one of our components is damaged or not. we've tried connecting multiple touch screens to other pies as well as ours but the same results follow. does anybody know how to resolve this ? any help is much appreciated