The clicking sound is usually the small fuel pump doing what it is supposed to do.* I would guess you are not getting ignition and that could be either low voltage, a*failed voltage regulator*or a controller problem.* Also check any fuses and connections on or near the heater.*
Fault isolating the controller unit isn't something most of us are capable of doing.* On my Espar D3 I had to remove the controller and send it to a service shop to have it checked.* In my case I ended up replacing the controller with a newer version.* That required some modification of the wiring and the removal of the external heater voltage regulator.
The service dealer I used was Boat Electric in Seattle (http://boatelectric.com/