Không hỏi giờ anh ấy : do not ask him FOR the time! (not accepted: do not ask him the time)
đừng hỏi giờ anh ấy: do not ask him the time! (not accepted: do not ask him FOR the time)
so confusing and frustrating haha
We've deleted this sentence long time ago and replaced it with "Đừng hỏi giờ anh ấy". This may be an error related to the system.
You should use the second one because it's more natural.
It still shows up when you practise the skill with a timer!