Mr Dan caught it.......it’s the water heater cover, not the furnace. I was just focussed on getting you the contact info.
BTW......I can’t zoom in enough and keep it in focus, but are you still using the white plastic locking tab to keep the door on? Not sure if it wasn’t locked properly and that’s why you lost your door, but the plastic ones will age from the sun and get brittle and break. I suggest you replace it with one of these available at any decent RV dealer shop.
https://www.amazon.ca/Camco-09213-Ca.../dp/B0006JLVFI
__________________
Ken and Terry
2018 Sunseeker 2430S-CD, nicely modified and carried by a 2017 Ford E450 Sport
Former Georgetown 330TS owner for 10 years with more mods than I can count, pushed by our 2017 GMC Terrain