DNS Issues After Updating to V6

[smurf]

@PromoFaux

During the upgrade operation, you will be presented with a dialog box asking if you wish to disable lighttpd. Doing so is probably appropriate for most users – unless you are using it to host web pages other than Pi-hole’s, in which case you may choose to keep it enabled. With lighttpd disabled, pihole-FTL will attempt to bind to ports 80 for HTTP and 443 for HTTPS. If there is any conflict on these ports, then it will revert to port 8080 for HTTP

I'm not sure if you disabled lighttpd during the upgrade, but try a couple things
https://yourIP/admin
http://yourIP:8080/admin