Unfortunately, we are in the solid state control era when thousands of homeowners are learning to clean their sensors. A slight coating of household or industrial contaminants coats sensors and makes the control 'think' there is no flame, so it shuts down. A little rod connected with a wire from the control board sits over the burner to sense when the flame is there. If the rod is coated, or the control board fails, there is no heat and it is time for the serviceperson to make a living. There may be other problems with draft as well, so it is beyond the skills of a handyperson.