Keeps kicking out of full screen

Up until today I was playing the game fine. As of today I start it up. It usually starts the loading screen in Windowed mode, then I click in the window and it loads up full screen. I did that today, it tries to go to full screen, but then boots me back to the desktop.

Every time I try to click on the (still running) icon for the game in the task bar, the screen flashes like it's trying to go to the full-screen game, but then it just goes back to the desktop. My NVidia Container icon pops up telling me that my monitor is optimized for 2560x1080 and I should set my resolution to that, but it IS already set to that (I never changed it from that in the first place).

I haven't updated or changed anything I know about since last night, when the game ran just fine. I can't even try playing the game in windowed mode now (not that I think I would) because I can't get it to stay in the game long enough to even try pressing Alt-ENTER (assuming that would even do it). It just kicks me right out, after flickering for a second or two trying to go.

It's still running there in the background; I hear a moment of sound from the game while trying to switch to it, but... no dice. I've tried changing my resolution to see if that fixes it, but that doesn't work, either.

I've got an Alienware m15 R4 with an NVidia RTX 3070. It's fairly new and I'm having no other issues I know of; and again, this game was working just fine last night, and I'm not aware of any updates that have happened. So... any ideas?