Hi!
I had a H170 MB and it had some problems - it started failing to find the monitor more and more often. It started crashing on boot and at the end could not even find the SSD on that SATA port. I thought it was a MB issue so I sent it back (it has 1.5 years of warranty left). In the meantime I got a 200-series MB (GA-H270-Gaming 3, Socket 1151) but when I connect only the essentials (PSU to MB, no GPU, no HDD, SSD or whatever) it cannot start. When you press the on/off button it starts for half a second, the fans begin to spin and that's it, it stops. On the the edge of the MB there are 4 LED's and one of them (for the CPU) is flashing. The MB is 200-series, the CPU is 6-gen (i5/6600k), it should not be an issue. I plugged and uplugged everything. The CPU fan is properly connected and starts spinning...for 0.5 seconds, like all other fans. It's not a PSU issue either.
Aside from a bent pin or spilled thermal paste (both of which are not the case) - is there anything else I can try before sending them both for warranty repair? A test with a different CPU is obviously my next task, but that's going to be in the coming days. Any ideas? Is it possible it was the CPU all along? Or is it a faulty socket issue?