Don't know what but the latest update isn't passing on requests to my defined pihole servers in /System/Settings/General.
Previous version works as expected.
I just updated to 24.7.12 and AdGuardHome not playing well. Reinstalled AdGuardHome v.1.14 after looking for repository update. No help and no access to local AdGuard webpage. Went back to Unbound now for temporary relief.
Not working is pretty vague... And the DNS server used is not even mentioned.
You can start by checking that pihole is working as expected.
Then from OPN, check IP connectivity to DNS server, check DNS resolution (interface diagnostics for both).
Then from a client, nslookup with default server and then specifically targeting the server that should be used.
In the process, check the live logs.