Not starting up after hard drive replacement

I purchased an iFixit SSD replacement for the internal HD on my late 2012 iMac that was starting to report bad sectors and would not run properly. The SSD install went without a hitch and the last step before reattaching the screen I hooked the cables up and tried powering it up. The internal fan comes on and I have a green led near the bottom center of the logic board that illuminates but I get no startup chime or any display activity. Can anyone point me in the right direction for a possible solution?

Just figured out that the LED that I thought was lit is actually 3 diagnostic LEDs 1, 2 and 3. The top one, #4 is not lit