This error will occur within a web application when any of the following conditions are met:

The database username is incorrect;
The database password is incorrect;
The database name is incorrect;
The database location is incorrect (the correct setting is localhost for most of our services); or
The database server is unavailable.

Ensure that your database information is correct, and then try again. If the problem persists, contact your hosting technical support and they would be more than happy to assist you.