I recently purchased one of these combos from buydisplay.com. I have tried everything I've read on here to no avail. I'm using the shield but checked my voltages anyway and they are good. I think I've modified the libraries as mentioned in other posts. (But honestly I'm not sure about that.) I'm trying to use the examples that come with the libraries so I won't post them, under the assumption that if your familiar with this topic you've come across the examples before. That said I will add them if someone asks. The site says everything one needs to get this display up and running in 10 minutes. I've been at it for 3 weeks. So odds are it's user error.
This is the exact display and shield I purchased if it helps https://www.buydisplay.com/default/7-inch-arduino-touch-screen-shield-ssd1963-library-for-mega-due
If anyone could break down the process to get this display to work (as if you were explaining it to a child apparently) I would appreciate it.