/emote takes his sword to cut this gordian knot
Please write down full specs, cant really say whats there.
First of all, I would disconnect everything and start from the beginning.
Take a simple ruler and check distance between board and components, it helps a bit in cases like yours, when you don't have much options in cable management.
If you have some black isolation tape (the electrical type) that would help a lot with cable management.
Until you give all specs it's hard to say anything for sure.
There are many reasons why the PC doesn't even power up.