http://nmcheck.gnome.org/ should not redirect to https://nmcheck.gnome.org/
We received a report here about a problem with nmcheck.gnome.org. The reporter says http://nmcheck.gnome.org/ is redirecting to https://nmcheck.gnome.org/ but NetworkManager understandably does not follow the redirect. Although redirecting from http:// -> https:// is usually important, this particular domain probably requires special handling.