Could this also mean 'What is his/her answer?' I tried the former but it wasn't accepted.
In English, I would say, "what is the answer?" what is her answer" but never "what is its answer".the term "its answer" is not used in English. "It" infers an inanimate object which cannot answer.
It's a perfectly possible thing to say in English, especially if "it" is a question. Or even better, if "it" is a Magic Eight Ball!