G15 5510, HD22Q dock, doesn't recognize P3421W, Latitude does

I'm having a recurring problem with my Dell HD22Q dock (the one that lets you charge your phone on it) and my Dell G15 5510 in which my system doesn't recognize my external monitor (the P3421W - 34" curved monitor) but does recognize the other peripheral devices that run through the dock.

Some background. I have a work Dell system (a Latitude laptop) and the G15 that I'm having problems with. For both, I use the USB-C connection from the dock to connect the laptop. For the work laptop, the dock feeds power and connects the display, my wireless keyboard and mouse, and a Dell webcam and I've never had an issue with it.

For the G15, the USB-C connection connection does all of the above except provide power, so I just connect the power supply directly to the laptop. The laptop usually lets me know on boot that the USB-C device is not providing power.

It works great most of the time, but over the last year or so, the dock will connect everything EXCEPT the monitor. It does not detect the monitor or acknowledge it in any way. When this happens, I usually do NOT get the warning from the laptop about the USB-C device not providing power. For a while now, the problem eventually fixed itself and I was never sure why. I assumed something just updated in the background.

This week, I get the warning boot screen, but now the monitor is not detected. I've updated the firmware on the dock, updated Dell Display & Peripheral Manager, cycled the power, and checked all the connections. I tried to update the monitor firmware via Dell Display & Peripheral Manager, but got an Error 4 every time.

Every other peripheral connected to the dock works except the monitor. I'm not sure this is going to fix itself the same way this time because when it fixed itself in the past, I got the warning screen on boot.

Any thoughts on how to fix this? TIA!