I've never had any problem with the speech recognition, that's actually my favorite thing. This is a direct translation issue. It has done it across all three languages I'm doing, on certain answers. My answer is identical to the correct answer, but it doesn't accept it as such.
Oh, I'm sorry. I could have sworn you wrote that but clearly I misread.
If this happens consistently and restarting the lesson doesn't help, I'd try both "The man is drinking." and "The man drinks." - including the periods, since older Duolingo sentences might occasionally have punctuation-related bugs.
And if that doesn't help, honestly I'd be out of ideas. My only other suggestion would be to post in the troubleshooting forums for help.
(Also, an error report or a screenshot might be helpful, so that I can send it off as a bug to the developers.)