Surely one can translate Iuppiter as Jupiter. Duo doesn't seem to think so - he marked me wrong!
Report this one, then -- I've normally been able to use Iuppiter and Jupiter interchangeably, at least in the English translations.
Oh, it just occurred to me: this looks like an English-to-Latin translation. You normally can't use anglicized spellings like "Jupiter" in the Latin translations, just as you can't change "Stephanus" to "Stephen" and expect it to work.