If a visitor tries to access a nonexistent subdomain or a subfolder they may be redirected to the default WordPress user registration page.
This issue is typically seen when a visitor arrives at the non-www version of the Multisite where the www version of the domain is primary (or vice versa).
NOBLOGREDIRECT can be used to redirect the browser if the visitor tries to access a nonexistent subdomain or a subfolder. Open a support ticket and our support team will add this line to your wp-config.php file to define your redirect destination:
define( 'NOBLOGREDIRECT', 'https://www.domainname.co.nz' );