PC won't boot, don't know why. Need help.

[That Guy In The Shirt]

So me and my friend were tinkering with his build trying to see if we could get the LEDs to work right in it. We found out that we couldn't sync the LEDs on his case and on his fans because the LEDs on the fans were built in (it was his build so I wasn't sure if that was the case until we looked at it). We didn't touch anything except for the LED controller and the psu (just turned the switch on and off when we were working with the pc). But for some reason, now when we turn his pc back on, his monitor doesn't register a signal on the Displayport setting, even though we never even touched the Displayport cable running from the gpu to the pc. Also his keyboard and mouse, which used to light up regardless of whether or not the monitor displayed anything, no longer turn on. We can't even get the BIOS to display. I tried restarting the thing, plugging the Displayport cable out fo his Asus PB278Q monitor and plugging it back in, as well as pulling it out of his gpu and plugging it back in, I switched the USB ports that the keyboard and mouse were using, and still nothing is working? Does anybody have any idea why the BIOS won't boot? The psu is still supplying power to everything, since his gpu fans are spinning, the mobo's lights are still on (so I don't think we somehow fried it), all the case fans are spinning, all the LEDs are working. Everything looks normal. Could I have done something to his cpu somehow? Or could something else be the problem? Any help would be appreciated.

Edit: nevermind sorry, I got it to work by changing the placement of the RAM (which he took out for some reason).