Blogs Directory – 'next' not working

I’ve got a multisite subdomain domainmapping network with about 90 sites.

on the primary site I’ve got the Blogs Directory plugin with ‘Sites’ as my home page and displaying links to subsites. However, the ‘next’ navigation doesn’t bring up a ‘next page’, the original page reloads. Tried with 5, 20 and 50 sites, no luck.