Volume controls not working

Hello! My Xfinity xr15 remote isn't working. When I press down on either the volume controls or mute button, the light just turns red. It is not low battery because the remote control is at 96%. I have tried resetting the tv box and re pairing the remote but it doesn't work. Everything else like channels and buttons do work. The volume only works if I use another remote that is not meant for X1 but changing TV input. My xfinity tv is updated too. Please help