I have been using my stove for a few years with minimal issues. It's been warm so I haven't used it in a few days. Today I tried to use it and it won't turn on. My house is now 64 degrees. The temperature on the thermostat is set at 72 and it just says READY. Why is it not going on? There are pellets in the hopper. The lid is closed. The door is closed. It is plugged in. What am I missing??? Thank you.