www.ultimatehandyman.co.uk

So the light is only switched on from one place!

Take a look at the first switch, the one that does not work and see which wires are in L1 and L2 then at the dimmer put one of the same coloured wires into common and the other one into L1 ( so if you have red in L1 and blue in L2 then at the dimmer put Red in common and blue in L1) the wire that is no longer needed, probably the yellow wire as you said it is not used should be well taped up with insulation tape, better still remove the yellow wire from the switch that is no longer used and tape it up there as well.

If it does not work then the dimmer is probably knackered, you can put the switch back on and try that, the light should then work.

If it was working before you screwed it up tight then it must have been a trapped wire that caused it.

But do make sure that the wattage of the light/s doesn't exceed the wattage rating on the dimmer switch.