Remove the batteries from the Xfinity remote
Press and hold any button on the remote for 5 seconds
Reinsert the batteries
Press and hold the Setup button until the LED changes from red to green
Enter the remote reset code for your model if required
Pair the remote again with your Xfinity box or TV
If needed, perform a factory reset by removing the batteries and holding the Power button for 10 seconds before reinserting them