翻译：You have no interests.
Why use plural? Oxford Advanced Learner's Dictionary gives one example: By that time I had lost (all) interest in the idea. So I think singular is also ok.
如果是複數那應該是，"你什麼興趣都沒有." "You have no interests" is just grammatically correct however it does not directly translate from "你沒有興趣." 正確的應該是 "You don't have an interest."