दरवाज़ा बंद नहीं होता है। or simply दरवाज़ा बंद नहीं होता।
बंद होना is a compound verb meaning 'to close' that comes from the adjective बंद.
Note: You might have noticed that this is a similar construction to when you are making general statements (which is where you've encountered होता before on Duo). Of course, in context, everyone will definitely understand that you are referring to a single door and not making a statement about all doors. But if you want to avoid all ambiguity, you can use यह दरवाज़ा/वह दरवाज़ा instead.
This ambiguity is only in the simple present tense. In other tenses (eg: दरवाज़ा बंद नहीं हो रहा है - The door is not closing), there is no ambiguity.