I've had a couple of issues with my DM4 that resulted in it not turning on.
First was the membrane (bit that you turn the gun on with). Replaced that, just call Dye for some free ones. Just have to slide the connector from the board and then unpeel the bit you press to turn on the gun and presto.
2nd thing was the one of the wires from the battery connector had snapped at the connector to the board. Again, I called Dye and got a new one free.
So as stark said, phone up, ask for those 2 things, replace 'em and then see if it works. Doesn't cost anything at the end of the day and Dye are very nice people to talk to. Do it before buying a new board.