Code upload issue with 2 computers

Hi all
Got an odd one I can’t figure out. Got a project written by someone else and is known to work. It for a mega with tft shield and touch tft screen. I tried to upload it via a win 8 laptop which compiled ok and uploaded with no issue but the screen is blank and only the back light is on. Got the same ide version and same libs installed on another win 8 laptop at home and completed install work and screen comes to life and all works as expected.just to check I responded from first pc and goes on ok but black screen.
I really can’t figure out why or how to find out why.
On a side note I used to upload from a mac and all was good but that has been broken now for a bit by Apple. Does anyone know a fix