How to connect to new RDS user?

Hi, I am using the AWS RDS instance. I have created a new user and new database but can't login using the created password.

When I use Sequel Ace with my master user it is all working fine, I am able to see the new database and username with privileges for the same database {{ database_name }}.*:ALL.

The problem comes when I try to login with the new user, using the same configuration settings, just changing the user name, database and password. The error is MySQL said: Access denied for user ....

Can you please advise what I might be missing?