Board Thread:Support Requests - Getting Technical/@comment-15409201-20200526040059/@comment-27958705-20200527141047

it looks like $wgNamespacesWithSubpages server variable doesn't include the main namespace (default mediawiki behavior). that means your page's name is exactly Items/Serum_Medium-Size_β, not subpage Serum_Medium-Size_β of page Items.

i believe staff can change it, if you will ask them (special:contact).