The router I am using is R7000, firmware V1.0.11.100_10.2.100. I saw somewhere that one of the latest updates to a Netgear router may be affecting Pi-hole, but I am not for certain.
You have a connectivity problem on the Pi-hole host, and clients on the network cannot connect to Pi-hole.
*** [ DIAGNOSING ]: Networking
[✗] No IPv4 address(es) found on the eth0 interface.
[✗] No IPv6 address(es) found on the eth0 interface.
[i] Default IPv4 gateway: 192.168.1.1
* Pinging 192.168.1.1...
[✗] Gateway did not respond. (https://discourse.pi-hole.net/t/why-is-a-default-gateway-important-for-pi-hole/3546)
*** [ DIAGNOSING ]: Name resolution (IPv4) using a random blocked domain and a known ad-serving domain
[✓] target.smi2.net is 0.0.0.0 via localhost (127.0.0.1)
[✗] Failed to resolve target.smi2.net via Pi-hole (192.168.1.8)
*** [ DIAGNOSING ]: Setup variables
PIHOLE_INTERFACE=eth0
IPV4_ADDRESS=192.168.1.8/24