If by "no click" you mean at the thermostat, then it's a thermostat problem. Depends on which click you're referencing.
The trouble shooting guide for my Atwood is surprisingly good. It takes you through what's necessary for everything to function, as it happens in the furnace system, step by step. It makes it fairly easy to isolate the problem.
No thermostat click means the thermostat isn't functioning. Thermostat working, no fan can be fuses or relays. Fan turning on but heat not firing means the sail switch isn't closing, either because there isn't enough battery
power to get the fan up to speed to blow it closed, or because the switch itself is failing.
That's as far as my knowledge goes. I've never had to trouble shoot the gas components.