It seems that Knights Visual material has been taken off of DMM, as I can't find the "oshaburi junbiko" series, or anything from that label on their site.
Their own personal webpage is still up and running.
From what I can see going by the box covers on their official HP, their titles do not have Ethics approval stamps. I recall DMM making a rule charge a month or two back requiring studios to have Ethics approval for their titles or they won't sell them so this could be why they are no longer on DMM.
Ethics cert per title cost a few hundred USD which may not be worth it for some companies if they're already making enough sales from people simply buying directly from them.