hey guys new here! I picked up a used greenfield and for the life of me I cannot get it to stay lit. I followed the directions in the owners manual and it goes out. I use a fire starter gel light the pellets and let them burn for a minute or two close the door turn the stove on and after 5-8 minutes the fire goes out and the stove goes into shutdown mode, while in shutdown mode the fire ramps up. What am I doing wrong!?!