I did Mensa nostra placet vobis and it didn't work
Verbs generally come at the end (they don't have to) but Duolingo is keen to teach orthodox syntax (except when it isn't).
I think the verb is usually supposed to be at the end, although I noticed that at other times Duolinguo doesn't like the verb at the end. However I believe in Latin the verb is usually supposed to go at the end.