I have over 30 devices but only 9 as of now are using pihole. The rest are "Device does not use Pi-hole". I believe it is because of this as well that things like my wireless cameras are not connected/working.
I have updated my router (TP Link Deco Mesh system) with my pihole IP. I recently installed unbound and am using it as my recursive DNS because only 3 devices where using pihole prior to this and using openDNS as a secondary DNS server, allowed all devices to bypass the pihole.