sitting down at the computer to start applying for jobs and naturally the computer doesn't fucking work.
seems like the same issue I've had once before where the PC is turning on just fine but the DisplayPort connection just Isn't DisplayPorting. Only solution is to turn everything off, unplug the DP cable from both the PC and the monitor, and then unplug both the PC and the monitor from the wall for an indeterminate amount of time, and then plug everything back in and see if it magically works again.
I don't know if this is the fault of my old graphics card or this old 4K monitor (by 4K monitor standards) but I know it's not the cable since the last time this happened I bought two more DP cables and neither helped, it's some sort of either static buildup or one/both devices' DP controllers getting stuck in a bizarre null state that can only be fixed by wiping their memory with a full disconnect and electricity fasting.
This is definitely what I wanted to spend this morning doing.