After assembly it wouldn't boot for over 5 minutes and hasn't given any beep codes, unplugged everything and reseated the CPU.
With no ram plugged in, and no GPU, it still refused to buzz out a beep code and required a long press on the power button to shutdown (all? mobos I've seen will shutdown with a normal press if they're erroring out)
Got no way to test the individual parts, it sounds like the motherboard is DOA, but gotta make sure before trying to return it.
Parts:
Asus Prime x370-PRO
Ryzen R5 1600
Corsair CMK16GX4M2A2400C16 Vengeance LPX 16 GB (2 x 8 GB) DDR4 2400 MHz C16 XMP 2.0 High
EVGA NVIDIA GeForce GTX 1060 Superclocked Gaming 6 GB
EVGA 750 W GQ Series ATX Modular Power Supply