I just discovered this and it works fantastically on any old / unused android device you might have lying around, I was shocked at how easy it was, all the instructions are there, once you have it running all you need to do is set your router DNS settings to your pihole IP address and presto! Ads and trackers are gone!
Sounds like your Pi-Hole isn’t set up properly then… Your Pi-Hole itself needs internet connection.
yeah, I’m not sure what part of the instructions I missed, though I’m not terribly knowledgeable when it comes to network setup.