I have installed and configured Pi-hole on a Raspberry Pi 4 with Raspbian OS. The Pi-hole DNS has a static IP 192.168.1.100. I am using the Wi-fi network.
I am trying to use it to block ads on my Windows 11 laptop but it is not working.
I would seem your router is advertising its own IPv6 address as DNS server.
Thus, devices may by-pass Pi-hole via IPv6.
You'd have to find a way to configure your router to advertise your Pi-hole host machine's IPv6 as DNS server instead.
You'd have to consult your router's documentation sources on further details for its IPv6 configuration options. Note however that some few router models wouldn't support IPv6 DNS configuration, and of those that do, a few show a misbehaviour of distributing their own IP address along with any custom address regardless.
If your router doesn't support configuring IPv6 DNS, you could consider disabling IPv6 altogether.
If your router doesn't support that either, your IPv6 capable clients will be able to bypass Pi-hole via IPv6.