To further add on to a necro post, in your router you should definitely have a secondary DNS address pointing to something other than piHole. If only the primary is present and pointed to the container, then if you stop your server effectively you have no internet access on any device using the router's DNS addresses.
Furthermore, within unRaid's Network settings you should not have it pointed at piHole. Rather you should have it pointed to the OpenDNS / Google's DNS. There are zero ads within unRaid, and using piHole for unRaid complicates things a ton more.