Please follow the below template, it will help us to help you!
Expected Behaviour:
After setting a single client manually, or the DNS setting on the router, DNS will resolve and ads will be blocked.
Actual Behaviour:
Either DNS will not work at all and no site can be reached, or sites load with ads.
This is a fresh install of Raspbian and Pi-hole after a bad SD card. When I test on one machine (Windows) by manually setting the DNS server, it will either load pages with ads or not resolve IP at all. I have updated Pi-hole, rebuilt gravity, and rebooted it several times all to no avail.
You have a setup problem. Your Pi-Hole is setup to listen at IP 20, but there is no IP address assigned on the ethernet interface where you have Pi-Hole listening.
Check your router and ensure the Pi is connected and with a static or reserved IP address. Note that address, then run pihole -r and select "reconfigure" to assign Pi-Hole to listen on that interface and IP address.
*** [ DIAGNOSING ]: Networking
[✗] No IPv4 address(es) found on the eth0 interface.
[i] Default IPv4 gateway: 192.168.2.1
* Pinging 192.168.2.1...
[✗] 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
[✓] bogeyandbirdie.com is 0.0.0.0 via localhost (127.0.0.1)
[✗] Failed to resolve bogeyandbirdie.com via Pi-hole (192.168.2.20)
*** [ DIAGNOSING ]: Setup variables
PIHOLE_INTERFACE=eth0
IPV4_ADDRESS=192.168.2.20/24