As far as I know, this is usually caused by a permissions issue in the database. That’s not something you did, it’s a technical error in the Softaculous integration.
To fix this, you can simply go into the MySQL Databases menu and create the database with the same name as the database created through phpMyAdmin. Don’t worry, it won’t delete the contents of your database. But it will result in the domain being added to the databases list.
You can do this through the control panel or through the client area. It doesn’t matter, they use the same code under the hood.