Check you interface listing behaviour, its not set to "Listen only interface eth0" . I hope you have connected your raspberry pi to the router via lan cable, if so please choose "Listen only interface eth0" and connect with a lan cable. I am not sure how well pi hole will work as a DHCP over wifi - even i am facing issues making pi work over wifi. With land and "Listen only interface eth0" it should work for you.
Also try to ping google.com or any other public dns to verify ping response after changing settings, if that does not work you may modify resolv.config temporarily to add a name sever to verify everything. Please do restart the services and settings and pi boot once done