Facebook log in keep redirecting in iOS

Question

I have an Unity application using Facebook SDK for user to link their account. Everything works in Android. But in iOS, the login page keep redirecting to the previous page which asking me to login even I press "Continue".

In my case, FB.IsLoggedIn return false so loginWithReadPermission is still being called and user fall in the loop between login and continue.

Are there any method to solve it, or at least get the error message?