Failed to load resource: the server responded with a status of 404 (Not Found)

[victoire barh]

Hello. i need your help please. I create an app that manages the library so I use firebase for the backend then the app includes the auth party and if I look in the firebase server I find the users connected with their email addresses but curiously the books are not saved in firebase.database. and when I inspect the page I receive this message "Failed to load resource: the server responded with a status of 404 (Not Found)"