I dig up this conversation because I had the same issue with a newly installed pi-hole.
I turn off all devices at night, included the pi. So the pi-hole need to restart correctly each day. After one week trying, I finally succeeded! It's a dirty solution but it work, maybe some of you will find something more clean.
For me, pi-hole can't work as a DNS server when restarted because he don't have the right time.
So :
1/ I installed ntp on the Pi.
2/ I forced "nameserver 8.8.8.8" on /etc/resolv.conf
3/ I change the right of this file to 555 to avoid system modification each time.
After each start, the pi need a bit of time to sync with ntp server but after that, all good to go.
1/ I installed ntp on the Pi.
2/ I forced “nameserver 8.8.8.8” on /etc/resolv.conf
3/ I change the right of this file to 555 to avoid system modification each time.
This has got to be the stupidest thing ever. So time goes off and internet doesn't work.
You cannot manually set the time. You cannot edit the file for the name server. You cannot install NTP.
Last time power went out the only solution was to wipe the pi and install it again.
Pi-hole since version 5.0 (May 2020) no longer changes the nameserver assigned to the Pi-hole host device.
If your Pi-hole host is using Pi-hole as nameserver, you change this in the OS and the host will have access to a DNS server whether Pi-hole is operating or not.