See “Error establishing a database connection”? Check the site, DB name, user,...

https://www.a1bookmarks.win/start-with-quick-checks-check-your-site-url-login-details-and-server-status

See “Error establishing a database connection”? Check the site, DB name, user, password, and host status first. Then try deeper fixes for bad files or tables. If you cannot access the DB, or it stays down, contact your hosting team right away for help.