HI - I have the same problem....
I placed the Master dimmer at the door/room entrance with power being supplied via the switch-live (TC&E) from the ceiling light JB (Live to Live, Switch-Live to Load), and 3C&E cable connecting the single Master to the first Slave and a further run of 3C&E connecting this 1st Slave to the 2nd Slave. All the "Brown" wires are wired to the Live terminals in each unit (although according to the instructions this is optional) all the Black wires are connected to the S-Link terminals in each unit and all the grey wires connected to the load terminals in each unit.
Anyways - I switch on the lecky and all appears well, the blue lights are on all the dimmer buttons and they all operate the main light lovely, all switch it on and off and all dim and increase light where the other one left off. Even the remote control that I bought worked the lights fine. I go off and then return 30 minutes later and none of them work. I could not get them to work. However the blue lights on the buttons are still on all dimmers, so they are all getting juice. So I turned off the electricity and refitted the original dimmer and that works, I then re-fit the Master dimmer and the lights work fine again from all units, I must have then tested them for 10 mins trying all the configurations with Master and slaves, all was good. I switch off and leave it for 15 minutes, come back and they don't work again!.
Any idea what could be causing it to work for a while and then not work even though power is being supplied? The Master is rated for 400w and I got 360w in incandesent bulbs on the light fitting, so I am assuming that it can't be overloaded. It says something (point 5 on page 2) in the IFU about ensuring the earth wire is properly sleeved, which I did. However, perhaps you can tell me if what I did was OK. Basically the earthing point on the back of the dimmer switch is woefully small, and I am expected to put the earth from the 2C&E, the earth from the 3C&E and the tail from the metal back box into it and there is not the room, so what I did - I put these 3 earths into an block connector and fed a single earth from this bc to the earth terminal on the back of the switch. Could this have caused said problems? Any help you can provide would be good since I have tried contacting Varilight but they do not respond - useless customer support. Cheers:banghead: