Please try and find the actual database error message of your connection problem, and then check it against the common error messages described in this topic:
If the error message you’re seeing isn’t in that topic, or you’ve double checked everything and still it doesn’t work, please share the error message and configuration (without passwords!) here.
No, it isn’t. Database names are in the format <username>_<database_name>. For example epiz_32335727_mydb. Please check the list of databases in the client area or control panel and make sure that you’ve created a database and are using the database name exactly as shown there.