No Internet through PiHole

Expected Behaviour:

Set Pi Hole as DNS server in router settings, internet works and devices use Pi-Hole without adds. have 2 pi-holes because router requires 2 different DNS servers

Actual Behaviour:

devices connect to the router but with no internet, cannot access any web pages and Pi-hole says nothing is using it.

Debug Token:

From Pi-Hole 1
https://tricorder.pi-hole.net/BqdIaKvk/
From Pi-Hole 2
https://tricorder.pi-hole.net/r4NiIrF9/

Your router is offering itself as DNS server:

domain-name: "lan"
      dns-server: 192.168.1.1
      router: 192.168.1.1

From a client that you believe should be connected to the Pi-Hole for DNS, from the command prompt or terminal on that client (and not via ssh or Putty to the Pi), what is the output of

nslookup pi.hole

nslookup flurry.com

nslookup flurry.com 192.168.1.251