SQL 2017 Access to DB

Hi,

I created a new database recently.

I created a different account (AD) to access the database for and admin that is setting up the app that will connect to the DB.

The user account is in all roles.

When they try to connect get login failed error 18456.

Is there something I am missing and can I test access using same account?

I am new to setting up Databases.

Thanks