Can't connect to MySQL server on 'mysql' (9)
Error establishing a database connection
This either means that the username and password information in your
wp-config.php file is incorrect or we can’t contact the database server at
mysql. This could mean your host’s database server is down.
- Are you sure you have the correct username and password?
- Are you sure you have typed the correct hostname?
- Are you sure the database server is running?
If you’re unsure what these terms mean you should probably contact your host. If you still need help you can always visit the WordPress Support Forums.