Hi jrichter73,
This problem struck my new main board again. In my case I used my cellphone Samsung Note 5 to test this issue. No-way, it did not work at all. I attached my Samsung Note 5 with USB cable to my laptop while phone is opened (as described at previous post). Laptop did not boot at all. Altough I waited almost 4 hours to boot, Laptop could not get off this merry go around. When I test this I also observed phone intermittently start charging, and stop again. There was very short duration of time USB power while I hit power button. This cycle continues several hours .
I think this problem is related to a bug in Peripheral Controller Hub chip of Intel.
Maybe, I am doing something wrong, could you attach a picture of your setup? so I can replicate the solution.
Any kind of idea are welcome!