|If the motherboard was previously working in your old case why would you suspect the motherboard? Why not suspect you did something wrong?|
I would pull the board out of the case and check the stand off placement. You should have the correct length standoffs installed beneath every screw hole but ONLY under screw holes.
If that is the problem and you are lucky both boards will be OK. If that isn't the issue then you need to test the boards with minimal hardware. PSU power connections only. CPU/HS/fan, 1 stick of RAM, video card, monitor and keyboard. No drives, additional cards, front case wiring, card readers, external hardware, etc.
Start the board by shorting the two power switch pins. Board should post to an error for no boot device.