"I do not turn on the light in this room."
I answered exactly that and was marked wrong. Some input from a native speaker would definitely be helpful on this one.
A verb that ends in ~ているis currently in the process of being done. For example, はしる is "I run" or "I will run," while はしっている is "I am running". So your sentence says you are not currently turning on the light, which is not the same as in this sentence, where the speaker has made a habit of not turning off the light in general.
Other than that, your sentence seems fine. The way Duo phrases the sentence, they do not turn the room's lights on in general, but your sentence can technically be read as someone who doesn't turn on the light when they are in that room (but perhaps may turn on that room's light with a different switch in a different room). That said, I think both are valid interpretations of the English sentence, and that both should be accepted as translations even if the nuance is slightly different.