I don’t run Pi-hole but quickly peeking into the container (docker run -it --rm --entrypoint /bin/sh pihole/pihole:latest) the folder and files belong to root with the permissions being 755 for the folder and 644 for the files.

chmod 700 most likely killed Pi-hole because a service that is not running as root will be accessing those config files and you removed their read access.

Also, I’m with the guys above. Never chmod 777 anything, period. In 99.9% of cases there’s a better way.