What do you mean by "it won't start"? If it is getting fuel, if the glow plug is good, it will start. Do you mean it doesn't even POP?
Is the tank pressurizing? Is fuel getting through the regulator to the carb?. If not, something is plugged up. Cold can aggravate these problems, especially if you have not been running the engine dry when finished flying and disconnecting it completely from the fuel tank.