Compress the top bezel a bit with your fingers (maybe hold the ipod in one hand but with the fingers at the top and bottom, instead of on the sides). Try to operate the Hold button. Does it work? If not, you may need to pop off the top bezel (it is held in with a mild adhesive - see the Step-by-Step Guides for pictures and tools) and check that there is no glue/dirt/muck on the contacts. If you do the removal carefully, there should still be enough glue on the bottom of the bezel, so you should be able to push the bezel back in and the glue strip should hold it in place. Try the hold button again. If that does not work, I don't know what else could be wrong.

I also had a white screen. I emailed ifixit support and Brady Cabe suggested I reseat the display connector. That did it!

One hint: when you reverse the steps, you will have to reinstall the top bezel but you don't have to completely reassemble the bottom in order to test it. The earphone plug can be left hanging out (avoiding wear and tear on the fragile ribbon cable) as well as the metal brace and the three screws that hold everything together at the bottom - that reduces the possibility of stripping the screws. In my case, I did strip one of the bottom screws: the screen was broken in a car accident that also bent the case enough to make it hard to get to one of the teeny tiny screws. Even though I stripped that one, I was able to get it out by turning it with a (tiny) straight blade screwdriver: there was enough purchase for that even though the head of the screw does not have much material left.