Infra red remote not responding, all batteries and settings checked

I am very familiar with the use of the Infra red remote controller. However, It has stopped working. I have not had any accidents with the camera or the remote controller and I have checked that the remote controller is powered and functional, I don't know what else can be checked. what advice can I get to sort this (recent) problem out? I have a Canon EOS 600D and an RC6 remote controller