Why won't my 3DS XL tun on at all?

Hey,

I followed a guide on this site to replace the circle pad from my New 3DS XL since the rubber was all in disarray. I took the one from my old regular 3DS and put it to the new 3DS XL. But I have gotten many results from putting it back together again.

1) It would power on, but It wouldn't display any pictures. Managed to scrummage around and fixed that which led to...

2) It would display the blue power on light, pop then turn off, managed to fix that.

3) Then I got to the point where the Botton screen worked and displayed, sounds went on, but the top screen was black, thinking that was just another ribbon fail, I popped the system open and tried to fix it. But that's where I am now.

4) The system doesn't want to turn on at all. It doesn't display the blue power on light, doesn't start up, nothing. It does, however, charge the battery, and displays a faint red light when it's plugged in for one millisecond and then disappear. This is my current problem and its been a week and a bit and I'm at wits end.

If I could get some help with this that'd be great. like I said, I'm really upset this isn't working. I just want my 3DS back.

Thanks in advance!