Try removing some parts. First unplug every USB device you have connected to that board and see if it turns on. Then do the same with the GPU. If that doesn't work remove all the hard drives. Finally remove both RAM sticks and check if it turns on and the fans start spinning. It won't post without the RAM, but it may proceed one step further. Finally use only one RAM stick and test it in every board RAM slot, one at a time.
All the previous issues are related and you may have a defective PSU or motherboard. The fact that these are new parts doesn't mean that they are working perfectly. You could try borrowing another PSU from a friend and testing your system with it. That way you'll know if the PSU is OK and then turn your attention to the motherboard. One easy way to know if the PSU can turn on, and isn't dead, is to do the paperclip test but it won't tell you whether your PSU is working perfectly.