This means WordPress can't reach its database. Check the credentials in wp-config.php first.
- In cPanel's File Manager, open
wp-config.phpand noteDB_NAME,DB_USER,DB_PASSWORDandDB_HOST(usuallylocalhost). - In MySQL Databases, confirm the database and user exist and that the user is added to the database with all privileges.
- If unsure of the password, reset it in MySQL Databases and update it in
wp-config.php.
If credentials are correct, the database may be temporarily overloaded or corrupted, try phpMyAdmin > Repair table, or add define('WP_ALLOW_REPAIR', true); to wp-config.php and visit yourdomain.com/wp-admin/maint/repair.php. Still failing? Open a ticket.