Hey Justin
I was having the exact same problem. I had it torn down to the point that you have it and was also confused as to why I was getting no voltage to the points that go to the power head. I even had an argument with the Dyson service tech over the phone, I was getting to the point where I was about to do my own soldering on the board to just put direct power from the battery to the power head brush….before I did this I decided to double check what the Dyson service guy told me, I cleaned up all the contacts with contact cleaner, even gave them a little brush with a piece of emery cloth. I did notice that the two contact points from the main motor body to the clear bin were pushed in a little so I slightly bent them out more so it would make a more solid contact. Low and behold it worked, the brush started spinning again. I feel really sheepish since the Dyson guy told me 9/10 times this was the problem but I refused to believe him since I was getting no voltage at those two points, anyways give it a try.