"Σε έχω δει."
Translation:I have seen you.
"I've seen you" is also correct; at the moment it is accepted as "a typo" whereas "I have seen you" and again "I have seen you" (identically the same) are given as the two correct answers.
All of your choices are shown as correct in the incubator. Why you get "a typo" is unknown. Are you on the web or the Android? Which area was this in: Strenghen skills, etc? Your input would help us clear this up. Thanks.