second GPU recognition issues

[Skordijhl]

I recently did some work on my rig, re-did some cable management and added some new fans, after i was done i put it all back together and turned it on. I have 2 780s and 4 monitors, (3) 23" i put in surround and (1)  40" to watch videos and what not, i have to have one of the monitors in surround on my second GPU and the rest are on the first. when i turned my PC on it only recognized 2 of my 23" and the 40" which are connected to my first card, i unplugged it, checked all the cables, made sure everything was connected but still noting was working on that second card. i then switched power cables to see if one of them was defective, still nothing, i then disconnected the first 780 from the mobo and ran  the second one and then it finally started displaying. after a few more shutdowns i got it all back to how i had before, not knowing what i did to get it to work. my question is why did that happen and how do i fix it in case i encounter this again later down the road.

[Pugs501]

Do you have a SLI Bridge?

[Skordijhl]

i had it connected the whole time except for when i disconnected the first card.