I have installed pi hole on a pi. My isp is running ip v6. I see in the log that ip v6 is not being blocked. My question is does my pi also needs an ip v6 address to block ads running on ip v6?
It depends on the level to which your network supports IPv6. If you run pihole -r to reconfigure Pi-hole, and you choose both IPv4 and IPv6, does it set both? If it does not find that you have full IPv6 support, then it won't add it and any clients trying to make IPv6 ad requests (through the Pi-hole) will seem to be allowed. This is because the response doesn't matter as the client has no real IPv6 connectivity.
Assuming your network and ISP have full IPv6 support, you should just be able to make sure Pi-hole is set up with both IPv4 and IPv6 via pihole -r, and then set the DNS on your router to the IPv4 and IPv6 address of Pi-hole (or use Pi-hole's DHCP server).
We also block IPv6 by default if you don't de-select it during installation. If @Mcat12's ideas don't help, generate a debug token and we can take a look.