Login in FireBase DataBase error.

I create a app with Login and Registration Screen but I only can use the Registration when I try to Login the app say “can´t find the user” please help me its my internship work.

Welcome. In order to help you, you will have to provide information.

Completing Peter’s answer, you need to detail your problem so that you can be helped by the members. Some possible problems: -the routine of registering the user: is he being registered? - the logic to search for the user in Firebase, was it checked? Show us the blocks.