I’m not sure how my computer got into this funky state, but I was playing around with a DEPNotify script, and after a while, I was suddenly getting these errors every time I tried to run it:

DEPNotify[12422:409983] Failed to set (keyPath) user defined inspected property on (DEPNotify.WindowController): [ setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key keyPath.

DEPNotify[12422:409983] Failed to set (backgroundColor) user defined inspected property on (DEPNotify.ViewController): [ setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key backgroundColor.

I tried rebooting my Mac. That didn’t make the problem go away. I tried creating a new user account, and that didn’t either. It didn’t matter whether I ran my script or just manually invoked DEPNotify with a single command. The screen would flash briefly, as if something were launching, but there was no DEPNotify window, and it wasn’t hidden or minimized.

When I did a Google search on the error, the only real results were someone not using the -fullScreen option properly two years ago and another case in which a script that starts DEPNotify just needed an update.

Unrelated to my problem (which I asked helped for but got no response), Arek Dreyer on the MacAdmins Slack (thanks, Arek!) was responding to someone else’s problem with the depNotifyReset.sh script. I didn’t run the script but tried to run the individual commands.

What ended up fixing it for me was sudo rm /var/tmp/depnotify.log and then killall cfprefsd. Then DEPNotify was functioning again!