"Miksi et halua ostaa tuota kameraa," is a correct translation as well
Yup, there are a lot of these alternatives missing for now. Did you report it using the flag?
"Miksi et halua ostaa tuota kameraa?" should be accepted
What's wrong with Miksi teillä ei halua ostaa...? What would be correct if you are talking to several people?
Correct form would be "miksi te ette halua ostaa"; your example would translate approx. "why do you not [have] the will to buy"
Miksi te ette halua ostaa tuota kameraa? would be correct for several people