No Power After SSD / RAM / Thermal Paste Replacement.

Recently picked up an iMac 27”, decided to swap the old hard drive for a 2.5” SSD, add 8 more gb of RAM, and swap out the thermal paste. I have a ton of repair experience, however once I put it back together (didn't put adhesive on the screen thankfully) it wouldn't boot.

It did boot and work before.

So, basically LED #1 is green, indicating it's getting trickle power from the PSU, but once I press the power button, I can hear buzzing from the power supply, and the 2nd LED doesn't light up.

Did I blow my powersupply? What should I check for next?