Translation:Please say it one more time.
Yes, another translation can be "Please, say it again," but no, "repeat, please" is not a good translation.
Many things can be repeated: a musical phrase, a carousel ride, a shot of whiskey, a back scratching session, a dance step. This sentence specifies 说; accordingly, the translation should specify "speak" or "say" (or some other equivalent).
If you use definitions, "this" and "that" just seem like opposites. But the way we use them, "it" and "that" can be more general, and "this" feels more specific. That's in English.
In Duolingo, it is teaching you specific words at this level, and it probably doesn't want you to use "this" or "that" because those are 这 and 那.
I'm not a native Mandarin speaker, but it also seems like 这 and 那 are less flexible, and the "it" is often implied.