I've been trying to get the monitor splits to function, but they don't seem to affect the application windows at all. I've got a single monitor connected to my laptop in portrait orientation, with a single vertical split. The separate task bars show up properly for each, and each taskbar accurately shows the windows open in that particular split. However, trying to maximize any window in any split causes it to maximize to the whole monitor. Additionally, when opening a new application in a split, the app launch window appears centered in the middle of the monitor (not the split), and underneath the taskbar of the other split.
Oddly enough, if I close an application while it is maximized and then reopen it, it will maximize to that particular split. If I then minimize it and try to maximize again, it then maximizes to the monitor instead of the split.
Any thoughts on any settings I should check?

You bet - it's attached. Let me know if you need more...

I've attached a screen recording of the monitor in question. As an example, if I make Excel fullscreen on my laptop monitor before closing it, it defaults to fullscreen the next time it's opened. So, if I open it while the vertical monitor has focus, it properly fills the split. Once running though, it will no longer maximize to the split.
As to the troubleshooting log, is there a particular section(s) of interest? There is a lot of personal information contained in that file, and I'm not comfortable sharing every single application that is running on my computer, all the directory paths of open files, tabs, etc.

Sorry for the delayed response, but I did capture the debug log and have attached it. The only difference from before, is I have three splits instead of the original two (the issue still persists). Let me know if you need anything else - -thank you!

Oh. My. Word. That did the trick! I have no idea how that would have gotten disabled, unless it was set that way by default. Haven't touched any of those settings in ages! Thank you very much, good sir!