Jisho.org Forum

Usually if you say just say もう一回 it will be enough of a prompt (if you're in person, adding some "I didn't catch that" body language will help).

When I am at work (in Japanese public schools) I say もう一回ゆって下さい　or もう一回ゆって下さいますか？
Those are long, but a little shorter and less textbook-ish than what you wrote. You can use 何? with friends or inferiors, but I've found
that THEY usually don't understand what part you didn't understand initially (or if you didn't hear, or if there was some other thing preventing you from catching what they said). Just like in English, 何 can also sound like you were not listening or something haha, so watch out for that. If I say もう一回言ってくれ？ it works better to get the part of the conversation I missed.

In my Japanese class, they encourage us to say 何でしたか？ rather than to tell the teachers directly to repeat what they just said.