[jsb5717]

Yes, could be main board. But could also be the diffuser. You'll need to disconnect the propane and pull out the burner assembly to check but a rusty diffuser will limit or just not allow the furnace to burn. It could also be the propane regulator. I had to replace ours for not flowing the propane at an adequate rate for the furnace requirements. New regulator solved it. I suppose it could also be the propane valve in the furnace. I haven't had one of those go bad so not quite sure what symptoms it would have.