Has he not started is what I answered. Can the perfect tense not be used?
I put "Hasn't it started?": rejected.
This question of translating the Irish simple past (preterite) by an English present perfect (have/has form) has come up several times, especially in sentences with some adverbs with a temporal aspect such as "fós","cheana" eg in this thread
Ar shroich sí an coláiste fós
Did she reachthe college yet?
Has she reached..." sounds more natural, in British English at least. but is certainly a valid alternative.
I have reported it in several of these cases and the have/has form is now accepted in some instances.
Of course, for the sake of getting through the lessons, once you know what Duolingo expects as the "correct" answer, you can just keep putting that, while understanding that there may be equally valid or better alternatives.
Is "Nár" used for all negative past tense questions? I presume that with using the copula vs. not there is a difference? And the irregular verbs?