Computer wont boot to windows/DOS after replacing PSU

[Dustybobs]

I Replaced the PSU on my wife's computer from a 850 Corsair PSU to a Corsair HX1200i because I'm upgrading her graphics in a few months going to need to extra power for the new video cards. Computer ran just fine with old PSU, after installing the new PSU all fans and systems seem to power on but i get nothing on screen. I've made sure than all power cables are correctly plugged in. I have tried resting CMOS. I tried HDMI and DVI cables to monitor. I seen a post where they advised to unplug the system and hold the power button for 30 sec to 1 min, that did not work. I'm lost as to why i'm having this issue with a bran new PSU but everything looks to be powering on.

 

[Dustybobs]

after troubleshooting I found that some how her old Graphics card is now dead as a door nail. I have no Idea how but once i pulled one of the graphics cards out of my computer hers fired right up.