This WordPress error means the site can't reach its database.

1. Wrong credentials: check wp-config.php (article 126) — the database name, user, password, and host (localhost) must all be correct. A recent password change is a common trigger (article 123).
2. Database user not linked: make sure the user is added to the database with all privileges (article 118).
3. Corrupted database: repair the tables (article 124).
4. Database server overloaded: high resource usage (article 171) can temporarily cause this.

Tip: Re-check every value in wp-config.php character by character — a single wrong letter in the password is the usual cause. If all looks correct, contact support@hostingpartners.co.za.