Why isn't my XBOX 360 Kinect sensor show the rest of my body?

Hello Dognut, thank you for reaching out to us. no worries, I'm here to help.

in order to assist you better please answer the following questions:
1. when did this issue start?
2.have you made any changes before it appeared?
3.do you see any error messages?

However, till you update me here are some troubleshooting steps to try:
1.make sure the Kinect sensor is plugged in correctly and try again.

2.update your console software:

-Insert a Kinect game disc.
-Start the game from the Xbox Dashboard.
-If your Xbox console software needs updating, you'll see the following message:
Update Required: An update has been found. To apply this update, you must restart your console.
-Select Yes, Restart to install the update

3.replace the cable

I'll be waiting for your updates to assist you further.
Best regards,
Adam.

How is my new Kinect sensor different from the Xbox 360 Kinect Sensor?

The new Kinect for Xbox One features a 1080p camera and can accommodate smaller play spaces than its Xbox 360 predecessor. It also features a 1:1 movement ratio with little to no lag.

Use of the Kinect sensor is optional with Xbox One. But some features, like automatic player identification and voice/gesture control, won’t work without it.

Can I use the Kinect sensor from my Xbox 360 on my Xbox One?

Like other Xbox 360 peripherals and accessories, the Kinect sensor for Xbox 360 is not compatible with Xbox One, and the Xbox One Kinect Sensor is not compatible with the Xbox 360 console.

forums.xbox.com/.../2060179.aspx

Not sure why the body text in my post isn't showing up...

This may mean that you’re having one of the following issues:

• The Kinect cables are not attached correctly.
• The Kinect sensor is not installed correctly.
• The Kinect is not positioned in a way that gives it enough room.

Try these solutions and see if any of them help

• Check the Kinect cable and make sure it is attached firmly to the console.
• Reposition the Kinect sensor to give it more space.
  
• Walk through the Kinect initial setup again.
• Recalibrate the Kinect sensor.
  

Unless if Microsoft makes an Xbox 360 adapter for the Xbox One, this may not be possible.

Xbox 360 Kinect games are programmed specifically for the 360 Kinect Sensor, and the Xbox One Kinect Sensor doesn't offer any sort of backward compatibility (afaik). It's likely the reason why there are virtually no 360 Kinect games
on backward compatibility.