Your debug log shows that Pi-Hole is working properly, responding to DNS queries.
This section tests Pi-Hole from the loopback address of the Pi and from its LAN IP, and verifies that Pi-Hole can reach an upstream DNS server.
*** [ DIAGNOSING ]: Name resolution (IPv4) using a random blocked domain and a known ad-serving domain
[✓] ad.doubleclick.net.34923.9239.302br.net is 0.0.0.0 via localhost (127.0.0.1)
[✓] ad.doubleclick.net.34923.9239.302br.net is 0.0.0.0 via Pi-hole (192.168.1.2)
[✓] doubleclick.com is 172.217.16.110 via a remote, public DNS server (8.8.8.8)
For the client on which are seeing ads, are you seeing matching client activity in Pi-Hole when you tail the Pi-Hole log at /var/log/pihole.log. For example, if you load cnn.com, you should see a query for cnn.com in the pihole log, followed by queries for a number of other domains for that web site.
This indicates that your clients are not sending DNS queries through Pi-Hole.