I think I’ve had someone use this driver to be able to monitor their Xbox, so you might want to just check in the Xbox configuration settings to see if there’s some option that needs to enable UPnP.
Whether or not a device is discovered via UPnP can depend on whether the device responds to the standard discovery search targets. Some devices may say they support UPnP, but they may only respond to very targeted, custom search strings.
There is another way to discover devices on your network, and that is through what is called mDNS (multicast DNS). This is an entirely different protocol than UPnP, but many network devices support it. I have an mDNS Discovery driver that I posted a while ago that you could experiment with if you are curious to see what it can find on your network. It’s just a general purpose query tool in its present form. I didn’t get much interest in it, so I never turned it in to any kind of ongoing monitoring driver like LAN Device Monitor.