Should this really be passive? What about "One can open it only from inside." The German is not passive, so the English should not be. Correct?
your answer is more common
That's definitely the more idiomatically correct version.
Would it be correct to say "Es kann nur von innen öffnen." ?
That's what I wanted to ask. Why is it "Man" when it is translated "it"?
It isn't, it's "one" in the personal sense, but the English and the German are not actually the same sentence.
Could "Man kann es nur von innen öffnen." be translated as "Someone can only open it from inside"? It feels like "one" and "someone" would give the sentence the same meaning in this context.
Why is there a need for man
The female voice seems to be saying "ihnen" instead of "innen".
The male one also does.
It's hard to distinguish between ihnen and innen. But I guess "from them" would sound odd here.
English is in correct for the German, should read "One can only open it from the inside." Please fix or replace German with an equivalent sentence.