"We are drinking his beer."
Translation:Wir trinken sein Bier.
Why would this be counted wrong when my answer is exactly like the response??
Since nobody can see what you wrote, referring to things such as "this" or "my answer" is not helpful -- instead, please quote your entire answer when you have a question, or even better, post the URL to a screenshot that you have uploaded to a website somewhere and that shows the question, your answer, and the error message.
My guess is that you made a small typo which you did not notice but which made your answer not exactly the same as Duo's preferred translation.
But without seeing what you wrote, nobody can say for sure.