The voice says: Τί λέει ο άντρας; with the o pronounced correctly, but when you select the o to answer, it says "omicron" instead of o.
ΝΟ, that's not how Duolingo words. Sentences are not rejected for lack of question marks or accents or anything like that. If your sentence was rejected there was a more serious problem.
Read the instructions here:
TIPS TO HELP YOU LEARN + HOW TO REPORT A PROBLEM
And check out the Greek Forum here with more links. https://forum.duolingo.com/topic/936