How to test GameCenter Leaderboards on ios?

I’ve implemented Game Center and leaderboards into my game:
Everything is setup as should be(Unreal Project settings, iTunes connect, Blueprints), but when I test it on my iphone, I get the message:

“Game Center Unavailble - Player is not signed in”

Is there a special way to test out GameCenter?

(BTW, I’m using a PC for development)

You have to create a sandbox user in iTunes Connect and then sign in with that user and enable sandbox on your iphone in settings->gamecenter. If I remember correctly I think I had to connect to a mac and use Xcode to enable the sandbox option to show up.