Look up DDU http://www.guru3d.com/files-details/display-driver-uninstaller-download.html and you may have to clean off any drivers and install what worked before.
Mixing cards has resulted in this (sorry but not vetting, linking today as I'm on travel) so we have to know about DDU and what version did work.
I've had a 3-monitor setup for a while, but just added 3 more monitors. While using the 3-monitor setup, I was using all 3 of my DisplayPort outputs on my GTX 970 GPU. The GTX 970 is only capable of 4 simultaneous monitors, so I added my old graphics card - a GT 730 - to support the last 2 monitors.
Basically, ever since adding the GT 730, my GTX 970 isn't allowing me to use more than 1 DisplayPort output at a time. Even if I disconnect all monitors from both GPUs, my GTX 970 only allows me to use 1 DisplayPort output at a time. Like I said, before adding the GT 730, I was using all 3 DisplayPort outputs on my GTX 970 for my 3-monitor display.
What's going on here?
Thanks

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