Yay! After 5 long years I've decided to upgrade my PC.
Long story short.
Old components:
Cooler Master mATX case
OCZ 600W PSU (OCZ600MXSP)
1 x SanDisk SSD
1 x WD HD
1 x EVGA Nvidia GeForce GTX 1060

New components
Ryzen 7 1700
Gigabyte AB350M-D3H
2 x 8GB G.Skill Flare-X F4-2400C
Crucial MX300 SSD

Outcome - power on, cooler led on, fans spinning, GPU fan starts-stops. Nothing else.
Funnily enough, power LED not turning on, HDD LED not active.

Took it back to PBtech assembled, they confirmed nothing wrong with my assembly, assumed mobo DOA and had it replaced. The new one was tested with my CPU but on a different machine, and had BIOS updated just in case, all in store. Worked just fine. Got home, reassembled - same story as before. Considering all the old components worked just fine in my previous setup, I suspect compatibility issues. Question is - which old component is the incompatible one.
Would appreciate any ideas, cause I'm at wits end.