U2715H, DP, can't see BIOS screen

You are right. Upon starting my computer today, it just went right back to not displaying the bios page so enabling DP 1.2 made no difference (although initially it did for some reason).

I have been doing some more experiments and I think I may have found the answer (I know I said that last time lol). I am using the HDMI port to connect my HTC Vive VR headset so I want to keep that plugged in but while I was having all this trouble not being able to get into the bios, I used the HDMI port to connect to my monitor as a second input.

Anyway, I disconnected the HDMI from the graphics card (Gigabyte RTX 2070 Super Windforce OC 3x 8G) and just left the DP cable connected. When I booted up, the bios logo was displayed and I could enter the bios again. As soon as I connected the HDMI cable, I could no longer see the bios.

Then it occurred to me, there was a gap between where my DP and HDMI cables were connected on the GPU. I had my DP connected on the far left, then the next port was left empty and then next to that the HDMI was connected. Maybe you need to have the ports connected right next to each other?

So I instead plugged the DP cable into the port on the right hand side of the GPU and the HDMI right next to it on the left so there was no longer any gap or empty ports in between the two cables. I restarted my computer and I could see the bios page with both cables connected.

I have restarted a few times now just to make sure and it seems to be working fine now. So I think this was the issue, I think you are supposed to connect your cables in a certain order on the graphics card but unfortunately the manual that came with it is terrible and didn't tell you that and on the graphics card itself, none of the ports are numbered to suggest which port you should connect to.

It seems that the order goes from right to left rather than left to right as I initially had it connected. So when you first turn on the computer, with the HDMI port being the first port it gave power to when it gets to the bios screen (in the order I initially had it set up and going from right to left), it will only display it on whatever is plugged into the first port that is occupied nearest the right hand side (in this case it was the HDMI port). If this port is empty then it will carry on to the next port along until it reaches a port with a connection, so the next one along would be the DP port. Which is why with only a DP connection it will display the bios screen but with the HDMI connected first, it would only show it on that.

However once it gets past the bios screen and it continues to load Windows, it ignores the order and will go straight to the DP as that is what I have set up in Windows as my main display. By instead connecting the DP cable to the first port on the right and before the HDMI port, when the bios screen loads it will immediately detect the DP connection and show the splash screen. Then once I am in Windows, I can switch to the HDMI port for my HTC Vive. The correct port order only effects being able to see the bios screen when you first boot up.

I hope I've explained that well. It turns out it's nothing to do with the monitor itself and was just because I had the order of connections wrong on the graphics card and you need to connect up from right to left.

If Gigabyte had provided a full manual instead of just a quick guide and explained that or even just printed numbers on the IO panel to indicate which port was used first, I wouldn't have connected it up wrong.

Thanks very much for your help though, I got there in the end.

I realize this is an older post, but for people looking for help, here is updated solution for those using older Nvidia cards. 

NVIDIA Graphics Firmware Update Tool for DisplayPort 1.3 and 1.4 Displays

Use normal good install practices: Clean boot, turn off your antivirus & malware apps.

Then run the firmware update.

Worked perfectly for my 980 / S3220DGF system.