"When do you go to work?"
Translation:Когда ты ходишь на работу?
You say на работе rather than в работе when you're at work, therefore you also use на работу for going to work.
The Tips & Notes for the "Where is it" skill have some tips on when to use на versus в, to some extent it just has to be remembered. https://www.duolingo.com/skill/ru/Where-is-it%3F/tips-and-notes
It is not so cut and dry. If you are focusing on the direction from one place to another, as in a destination, even if it is repeated, you can still use идти. Using ходить usually focuses on the round trip, which is why it sounds so odd here. I would say когда ты уходишь на работу, if you want to sound natural.
It's not just uni- vs multidirectional, it's also one-time vs repeated actions. "When do you go to work?" is typically about a repeated action, so would be translated ходить.
Russians typically say "ходить на работу", even if transport is used. "Ездить на работу" is used if you go by transport and the fact is important, if we're interested in how you get to work. I think the course creators have got this one right.
Please don't use profanity, even in transliteration.
I have asked, and have been asked, this exact question, in reference to a one-time instance. If I know someone has to work today, I could very easily ask them "when do you go to work?" to inquire as to their time of departure. I understand this sentence most naturally lends itself to a repeated action situation, but like I said, the English is ambiguous. It should allow for both interpretations.