"Do not drink beer"
Can't I report typos? This sentence should accept the singular form as well.
Yeah, at the moment, the reporting feature has reduced functionality. You used to be able to click on "other" and type what the problem is ... Duolingo is apparently on a temporary platform at the moment and hopefully when it's updated again, the ability to type something will come back.
The only way to get a message to the creators that something needs to be fixed when there's only one letter off and it decides it's a "typo" would be to write something like "You should be able to write 'usinywe bia' as well" and then click on "my answer should be accepted. They'll see it then and hopefully add it "usinywe bia" and not, like, the whole sentence that you wrote. :-P