While accessing the Joomla site I was getting the error as "Database connection error (2): Could not connect to MySQL"
1. Database Credentials in 'configuration.php' file -
Please make sure that database credentials that is database username or database password which you're using in your site's configuration file is correct.
2. Below are the field which you'll need to check in 'configuration.php' file-
public $user = 'MySQL_database_username';
public $password = 'MySQL_database_password';
3. If you are not sure about the MySQL database details please reset the password and give a try. In cPanel you can reset it from -
cPanel >> MySQL Databases >> Current Users >> Change Password
It fixed my issue!