DisplayPort troubles on Dell Precision M6700 (with GTX980m upgrade)

I’ve been running a 1080p/FHD external monitor over HDMI with my old trusty M6700 for years (somewhere along the way I upgraded the original K4000m to a GTX980m). When this monitor decided to let out the magic smoke I bought a 1440p/QHD monitor as an upgrade. I expected that to be too much to push over HDMI which seems to be correct (output limited to 1080p) but I thought DisplayPort should be able to handle it. However, when I plug it in, I cannot get DP to display anything on the new monitor at all.

Could the GPU upgrade be the culprit here? It’s been a while since I installed the GTX980m though and as I’ve seen other people with the same upgrade on this forum I was hoping someone here could point me in a good direction for troubleshooting or either at least affirm that DP should even be working at all on such a setup as I’m at kind of a loss.

The new QHD screen works just fine over DP on other laptops by the way.

 

Do you know what VBIOS your 980M has?

 

GPU-Z reports: 84.04.48.00.33

I should have mentioned it's a MSI GTX 980M (4GB). It's what I had available at the time.

 

I see, if you have switchable graphics (if you can see your Intel graphics in device manager) then you could flash a Dell vbios to it. Does Nvidia Control Panel say anything about the DP?

 

...Oddball thing that occurred to me is you could try nabbing a PR02X dock and using one of the DisplayPorts on the dock...
(I regularly use DP output off of a PR02X with M6700 + Quadro M5000M. Can't say that I've ever tried the DP direct on the system, actually.)

 

The integrated Intel and dedicated gtx980m card show up show up separately in device manager. With DP plugged in Nvidia Control Panel doesn't have anything useful to report (it doesn't think a display is connected at all). But when I connect over HDMI I think it at least acknowledges the existence of DP as another potential output of the card as DisplayPorts show up in the audio settings as well as the graphic for PhysX for what it's worth.

I'm hesitant about flashing a different vbios to the card. I'm very much a newb when it comes to anything but by-the-book flashes. I imagine that would give issues with the non-standard hardware of the card (4gb vram for the MSI while I think Dell only had the more common 8gb version).

I do use a PR02X already actually but both DPs in the docking station don't work either.