Xbox 360 Pair an XBOX360 wireless controller with XBOX360 after it has paired with Xbox One

[ling_xboxforums]

I have an Xbox 360 and an Xbox One. I purchased the Elite wireless controller to use with the Xbox One and an Xbox 360 wireless controller to use with my Xbox 360. For a brief period, it all worked as it should. Then for some reason, my Xbox 360 wireless controller paired with my Xbox One and I can't get it back to the Xbox 360. I have done quite a lot of searching and can't find this exact situation. I have tried plugging the Xbox 360 controller into my Win 10 PC using a USB cable. It did not work. I unplugged my Xbox One (otherwise it would power on) and went through the pairing procedure to try to pair my Xbox 360 controller with my Xbox 360 and it just times out without pairing. I plugged the Xbox 360 controller into the Xbox 360 (front and back) but it did not work. I would like to get my Xbox 360 controller paired with my Xbox 360 and keep it there. Thanks.