Literally ‘[At] what time and [for] what reason?’ (although Duolingo doesn't accept that yet).
Which hour and which reason?
Interesting and very specific way to ask when and why.
I'm finding these sentences a bit difficult because there is no real context to them. "When is the concert?", and "Why are you happy?" feel like more complete sentences.
What hour and what reason should be acceptable
What time and why? Not accepted; reported (16/VIII/21)
I wrote a typo and got it wrong. RIP