This indicates that the DNS queries are not going to the Pi-Hole. Use these tools in the thread below and they will help you determine why you are seeing ads. The query log and /var/log/pihole.log will have all the DNS queries received by Pi-Hole, along with the response from Pi-Hole. If you open a web page while you tail the pihole.log, and see no traffic in the pihole.log, then the DNS requests are going to somewhere other than Pi-Hole.