UPnP stands for Universal Plug and Play, which is a set of networking protocols that allows networked devices to automatically forward ports, avoiding the need for manual port forwarding. Xbox uses UPnP to set up your router for multiplayer gaming and chat. If you see the message "UPnP not successful" in your network settings, it means that there are issues with utilizing UPnP and failing to automatically forward the correct ports, which can result in connectivity issues with Xbox Live.

To fix the "UPnP not successful" error, you can try the following steps:

• Navigate to the UPnP menu on your router.
• Ensure UPnP is enabled.
• Disable UPnP.
• Save your changes.
• Restart your Xbox One, router, and modem.
• Navigate to the UPnP menu on your router.
• Enable UPnP.
• Save your changes.
• Restart your Xbox One, router, and modem.

If these steps dont solve the issue, you can visit Xbox One port forwarding guide for further troubleshooting.

There is some debate about whether UPnP should be enabled or disabled on Xbox. Some users believe that enabling UPnP can make you vulnerable to security breaches. However, UPnP is generally enabled on almost all routers by default and should be generally safe. UPnP is also necessary for achieving an Open NAT type, which is required for playing online games with other players.