Absolute newbie here so any help is greatly appreciated. Last Spring I did a basic standard install of Pi-Hole on a Pi 3+. Followed the instructions that I found on the internet and everything worked as expected, it was even blocking Youtube ads. Fast forward to July I tried running Pi-Hole in a docker container and it never did work, I couldn't even get docker to run properly. After a few days I gave up and rebuilt the Pi-Hole from scratch using the same on-line instruction as before. Now for some reason, it's not blocking Youtube ads. I've searched around for a bit and everything indicates that Pi-hole does not work with Youtube but, honestly, I went months without seeing any ads and it wasn't until I rebuilt everything that the ads started reappearing.
actually it can't because it's on the same host, not necessarily the same server.
Pi hole blocks based on host.
however,
Did you make a backup of your config before starting over?