Cannot select database

The database server could be connected to (which means your username and password is okay) but the 18th_clean_live_db database could not be selected.

• Are you sure it exists?
• Does the user 18th_user have permission to use the 18th_clean_live_db database?
• On some systems the name of your database is prefixed with your username, so it would be like username_18th_clean_live_db. Could that be the problem?

If you do not know how to set up a database you should contact your host. If all else fails you may find help at the WordPress support forums.