overnoise

It’s notice, not an error!

I think that the problem is this: https://core.trac.www.ads-software.com/ticket/17090#comment:19

it worked for me.

We had modifed the following code from the file “admin.php” in the path “/wp-admin/network”.

=========== Previous Code

if ( ( $current_blog->domain != $current_site->domain ) || ( $current_blog->path != $current_site->path ) ) {
wp_redirect( network_admin_url() );
exit;
=========== Corrected Code

if ( ! is_main_site() ) {
wp_redirect( network_admin_url() );
exit;

Same problem here. I’m trying to fix.