1. Just to check, you plugged that sabrent hub into the monitor, but where did you plug the monitor downstream usb into?
2. you said that the usb ports on the kvm do not work, correct?
3. It looks like that sabrent hub has power switches for each port, have you verified that they're on?
4. Can you describe what you have plugged into where? Based on your other comment about this working with an older monitor (which shouldn't affect the kvm's usb ports) it sounds like your configuration might be the issue.

not sure if this is the exact one but I have something similar to this. I paid ~~12 bucks for it, this is probably more expensive now because it's older/out of stock. I would recommend just looking for something similar rather than buying the exact same one at this price. I got it because it was cheap at the time, there's nothing special about it.

Something like this? Maybe there are others that support more devices.