It's not necessarily a new build, but I took components from a stock Acer computer and added them into a new case along with a new motherboard. Everything is compatible. The problem I'm having is that when I go to turn on my computer, the case fans and CPU fan will spin or "twitch" then stop. I'd tried to turn it on again, but the second time nothing would happen - no twitch, no nothing. The LED on my motherboard will be illuminated, but the computer's fans just won't spin. I haven't bothered to plug my computer into a display cause what's the point if CPU fan isn't even running? Unless you guys suggest otherwise. Any ideas on what's going on?
Alright I have seen this issue before, you might be shorting it, ensure that no wires are exposed and that you didn't accidentally screw the motherboard into the case itself without a mounting socket (the little things you put into the case that you screw into it I don't know the actual name). Its possible something else is wrong but I am not sure what else it could be.
It does sound like a possible short. You need to ensure you installed the standoffs between the motherboard and case. You also need to make sure all the standoffs line up with a mounting hole in the motherboard. An extra standoff can cause a short. The checklist in my signature was created to troubleshoot this type of problem. If you're sure the standoffs are installed correctly then perform EVERY step in the checklist and let us know how it goes.