Show 404 when someone visits a non-existant Multisite site

The option is in Network Admin, Settings, Network Settings, Allow new registrations

Network Settings Registration Settings

(screenshot from WordPress’s Managing a Multisite Network video)

You want either “Registration is disabled” or “User accounts may be registered”.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)