Dual Monitor Display no longer functioning

System Specs: i7-7700k 4.2GHz Quad-Core MSI Z270 Gaming M7 Mobo Samsung 850EVO 1TB M2 SSD Corsair Vengeance LED (2x8GB) RAM MSI GeForce 1080Ti Gaming X GPU

Setup involving old Gateway monitor (unsure model) and ASUS PG279Q that has been working for months suddenly decided to stop working today. Only thing I was doing differently than any other night was using my Headphones to run sound (instead of PG279Q built-in speakers) and playing League of Legends which I hadn't touched in years (and likely won't after this mishap).

Playing my game, suddenly both monitors turn off. I hear the disconnect windows noise in my headset, then the reconnect, both monitors turn on, no problem. My stream I was watching on my second monitor is now on my primary but I move it back over. Issue happens again. This time only the secondary Gateway monitor turns on, PG279Q says DisplayPort No Input Detected.

Restart my PC, only secondary turns on again. Same issue with the PG279Q. Go to windows Display Settings, it's showing two detected monitors, the secondary still set as '2' but the primary set as '1' now being much smaller. It is permanently locked into 'Display on 2' as when I try and change it to 'Extended' I get an error message.

I go to NVidia Control Panel, it shows both my Gateway and ASUS monitors, however the ASUS monitor has no checkmark in the tick box. I can not check it. Clicking does literally nothing.

Despite both Windows and NVidia Control Panel detecting a second monitor, I cannot switch my sound settings back to my PG279Q built-in speakers.

I tried switching the DisplayPort cable to the second slot on my GPU. Does not resolve the issue. I tried attaching the HDMI cable to my PG279Q and it did not resolve the issue UNTIL I reset my computer. I am now using my PG279Q on an HDMI cable but I would much prefer to use DisplayPort for the 144Hz refresh rate.

Considering neither port works on the GPU, NVidia and Windows pick up the second monitor when a DP cable is plugged in but do not allow me to make any changes to display on that monitor, and the fact that it works with the HDMI cable, I've come to the conclusion that it's likely either the GPU or the DP Cable. I do not have a second DP Cable to test but I will likely be running out to get one tomorrow if nobody has any ideas as to what the issue is; it's just an expense I'd rather not have to make.

I'm really hoping it's not the GPU as it is warrantied but that leaves me out a PC for god-knows-how-long as my previous PC just got replaced because the the GPU (among other things) went on it.

Does anybody have any ideas? A forum post I read said a Bios reboot might solve the issue which I'm going to try after this (but I doubt that'll solve the issue). I'll be grabbing a DP Cable tomorrow if nobody has any possible solutions and testing that. If any extra info is needed I'll post some extra comments/answer questions before heading out to grab that DP cable, but it's late at the moment after trying to troubleshoot myself and I'm gonna get some sleep.

Thanks in advance!

EDIT: Tried rebooting Bios, issue persisted... Left the Display Port cable connected though. Suddenly worked when I went to turn it back on today. Happy it's working but wish I knew the issue since now I'm just waiting for it to happen again...