From a client that you believe should be connected to the Pi-Hole for DNS, from the command prompt or terminal on that client (and not via ssh or Putty to the Pi), what is the output of
oh sorry that I was not clear enough the client that is still connected to the internet when I have the pi hole connected with the DNS is the raspberry pi that has pi hole on it connected to Ethernet, even though it is connected to the internet it still gets ads
This device is not using Pi-hole for DNS, it is using Google.
You may have mis-typed the command. Pi-hole answered the request, but you want to nslookup for the domain pi.hole (with a period).
This device (different than the first output?) is not using Pi-hole for DNS, it is using Google. If this is the Pi, then edit file /etc/dhcpcd.conf and change the nameserver to 127.0.0.1. You will see an entry like this in that file: