In this case, the internal gear of the lens should be misplaced or damaged. You can try to turn the lens by hand, but not too hard, then turn it off and put it on again. If not, please try several times, but be careful. Don't do it if the lens shakes a lot. Go directly to the dealer or local warranty point. This situation should be repairable, but generally a maintenance fee will be charged, ranging from 100-500. I have studied this kind of questions, and I can ask them if I have any questions (completely original)