Check the database settings in the config.php file. Maybe the server name is incorrect (try "localhost"), or there is a speeling mistake in the DB_USERNAME or DB_PASSWORD (password and user name are case sensitive!).
Install Adminer (
http://www.adminer.org/en/) on your webspace and check if you can login to the database with the values from the wb config file. If this doesn't work, you have definitively entered the wrong values and have to change these.