reply to Chilly
Re: today my heater will not start umless... Not familiar with that heater , but here is a guess .
For some reason the furnace is not proving flame .
When you remove and replace the door , a safety switch is cutting power to the unit .
This serves to reset the safety circuits when you replace the door .
You could check to see if this is the case by turning off power to the unit and then turning it back on .
In any case , you have an issue with the unit that should be looked at by a pro .