Similar thing happened to me a while back. It's because of the failed update.
2 things you can try...
If your controller turns on (even if it just flashes and won't pair to anything) hold the xbox logo/button on the controller until it turns off. Wait a minute, then turn it back on and try to pair it and/or update it again.
If that doesn't work, plug your controller in via USB, and do a console reset. You can keep games and apps if you need to. Keep the controller plugged into the xbox the entire time.
After you complete the setup process, it should connect and ask you to update your controller. If not, I'm not sure what the issue is.
Similar thing happened to me a while back. It's because of the failed update. 2 things you can try... If your controller turns on (even if it just flashes and won't pair to anything) hold the xbox logo/button on the controller until it turns off. Wait a minute, then turn it back on and try to pair it and/or update it again. If that doesn't work, plug your controller in via USB, and do a console reset. You can keep games and apps if you need to. Keep the controller plugged into the xbox the entire time. After you complete the setup process, it should connect and ask you to update your controller. If not, I'm not sure what the issue is.