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!
This could be a long shot but if it’s a Samsung Galaxy Tab S, the battery connector solder joints kinda die after a while, which can either be fixed by reflowing them or by applying pressure (I have a tablet with that issue). You could try pressing on the battery connector and see if it works then.
I looked a little closer at the battery connectors and when pulling the battery out I must have yanked the little wires out of the clip just ever so slightly (I could see a little bit of them reflecting on one side) I carefully pushed them back in and avast! There is life again! Thank you kind stranger!