It sounds like you may be dealing with an issue related to the airflow within your heating unit. When the door is closed, it seems the airflow is restricted, causing the unit to go into lockout mode as a safety precaution. This could be due to a variety of reasons, such as a clogged filter or blocked vents. I’d recommend reaching out to Oakville Appliance Repair for assistance. Their expertise in diagnosing and fixing appliance issues could help identify the root cause of the problem and get your heating unit back up and running efficiently.