OK.1st thing you need to do is go in to where the toilet cassette goes and remove the cassette.then look and see if batteries are fitted and good and making a good connection in the battery holder.Then if that is OK on the left half way along and down look for a plastic bit with 2 wires coming from it.that is the reed switch.using a known good working magnet put it up close to the read switch and get someone to check if led is on.if it is the the magnet may of fell off the float inside the cassette as it is common and you need to buy a new float switch and fit it
Caratech, October 2013