Resolve mysql DB connection error

This is an error when doing php artisan migrate.
SQLSTATE[HY000] [1045] Access denied for user 'user_name'@'host_name' .

The server is RDS.

DB_HOST=endpoint
DB_PORT=3306
DB_DATABASE=
DB_USERNAME=
DB_PASSWORD=

I think all the connection information is correct.

I think I can't connect due to a permission issue.

Please check and connect with TeamViewer.