Moved my new build into its new case and now it won't power on - Details

First of all, thanks for reading. Im posting from my phone so I'll be brief. Had my.build complete except it was still in an old shabby case. I got the new case in the other day and moved the guts inside. Once I had everything inside I plugged in and hit power only to get a microsecond flicker of the LEDs and then nothing. Subsequent power button presses didn't even show a flicker until power was disconnected and reapplied. I've taken the whole thing apart and reassembled it and still nothing. Pictures and specs to come. Reddit, I'm stumped. What are your thoughts?