Thanks! So "kuwa" is the infinitive here, not a command (imperative). If they wrote "to be here" as the correct translation above, it would remove this ambiguity.
I have never seen it explained before that "kuwa" is indeed used to express being in a place, just not in the present tense.
So the past tense would be "alikuwa hapa" (with "alikuwapo hapa" or "alikuwepo hapa" as more explicit alternatives)?
I can no longer see which lesson this question is in. I didn't realize that this is not shown if you read a discussion from outside the lesson: https://www.duolingo.com/comment/26419870
Isn't it in a Present tense lesson? (That would be why I objected to an answer in the imperative, which should be in the Commands lesson.) Or was I not concentrating?
Update: This question is indeed in the wrong lesson. This one is about the present tense, though it is packed with lots of tenses and moods, which confuses students who haven't done those lesson units yet. (Reported 15 June 2018.)
I can see that all possible translations should be accepted, but the course developers should fill each lesson with questions that do illustrate the topic of that particular lesson.