U2724DE USB-C not working for KVM functionality

I have a U2724DE that I'm trying to use with the KVM functionality, connecting a Windows 11 laptop and a Windows 10 tower.

Both the laptop and the tower work fine with the monitor when plugged into the Thunderbolt port.

However, when either one is plugged into the non-Thunderbolt USB-C port, the monitor doesn't recognize anything as being connected.

Right now I have the tower plugged in to DVI + USB-C, and the laptop into just the USB-C Thunderbolt port, with a U2724D being daisy chained off the DE via DVI (my desired setup).

Everything is fine and well with the laptop, but switching the KVM over to the tower, it displays my tower PC's desktop on the monitors, but the mouse and keyboard are still connected to the laptop.

When I run through the KVM setup process, it just says to plug the USB-C to USB-A cable into the second PC and won't let me proceed, refusing to acknowledge that it's already plugged in.

Unplugging/replugging does nothing, I've also reset the monitor to factory, tried other USB ports, and updated the monitor's firmware to latest, but it still can't see anything on the non-Thunderbolt USB-C port.

I also tried a different type C to type A cable but I still get nothing.

Is this possibly a bad port, or am I missing something here?