Stumbled upon this because I am having a somehwhat similar issue (moderator edit: to Unexplained Drop From 13% to 2-6% Block Rate).
nslookup pi.hole Server: 2600-0011-0f02-4319-0000-0000-0000-0001.res6.spectrum.com Address: 2600:0011:0f02:4319::1 *** 2600-0011-0f02-4319-0000-0000-0000-0001.res6.spectrum.com can't find pi.hole: Non-existent domain
nslookup flurry.com Server: 2600-0011-0f02-4319-0000-0000-0000-0001.res6.spectrum.com Address: 2600:0011:0f02:4319::1 Non-authoritative answer: Name: flurry.com Addresses: 126.96.36.199 188.8.131.52 184.108.40.206
my client IP 192.168.0.97 Pihole sits on 192.168.0.18 Router 192.168.0.9 DHCP running off the router range 200-254. WAN DNS setting on Asus RT-AC66U-B1 set to Connect to DNS Server automatically. Lan --> DHCP Server --> DNS Server set to 192.168.0.18 (Piholes IP). On the pihole running on RPI --> Settings --> DNS --> upstream DNS: Google (ECS) all 4 check boxes to the right are selected. listen on all interfaces is on. Advanced DNS Never Forward non -FQDN's and **Never forward reverse lookups for private IP ranges are both checked. Use DNSSEC is unchecked. Conditional forwarding is checked 192.168.0.0/24 IP address of your DHCP server (router) 192.168.0.9 local domain name: landsend. In network overview I see all clients are connecting to the pihole.
Is it normal not to get the "cant find Pihole" message?