Rebuilding with my son. New MSI H270, i7 6700k and 16g ddr 2133 (2×8g) double, triple and re checked again. No luck. Case lights, fans and board LEDs all work, but no boot. No usb ports work and no keyboard/mouse lights. Tried several times and used every available port but no change. No debug lights stay on but just won't boot.
Not that I think I can help, but you should be more specific for troubleshooting:
-what exact motherboard? (only H270 might be not enough)
-I assume old PSU is used... how old and which one?
-are you getting some error sound ("beeps") on power on?
-no boot means screen remains black after power on?