EDIT: Your Pi-hole seems fully operational for IPv4, receiving, filtering and forwarding queries (click for details)
*** [ DIAGNOSING ]: Name resolution (IPv4) using a random blocked domain and a known ad-serving domain
[✓] jeansporn.blogspot.hk is 0.0.0.0 via localhost (127.0.0.1)
[✓] jeansporn.blogspot.hk is 0.0.0.0 via Pi-hole (192.168.0.21)
[✓] doubleclick.com is 142.250.189.14 via a remote, public DNS server (8.8.8.8)
*** [ DIAGNOSING ]: contents of /var/log
-rw-r--r-- 1 pihole pihole 21345 Jun 25 18:23 /var/log/pihole-FTL.log
-----tail of pihole-FTL.log------
[2021-06-25 18:20:07.080 24829M] Imported 53518 queries from the long-term database
[2021-06-25 18:20:07.084 24829M] -> Total DNS queries: 53518
[2021-06-25 18:20:07.084 24829M] -> Cached DNS queries: 6128
[2021-06-25 18:20:07.084 24829M] -> Forwarded DNS queries: 35386
[2021-06-25 18:20:07.084 24829M] -> Blocked DNS queries: 11805
[2021-06-25 18:20:07.085 24829M] -> Unknown DNS queries: 0
[2021-06-25 18:20:07.085 24829M] -> Unique domains: 2625
[2021-06-25 18:20:07.085 24829M] -> Unique clients: 18
[2021-06-25 18:20:07.085 24829M] -> Known forward destinations: 1
*** [ DIAGNOSING ]: Networking
[✓] IPv4 address(es) bound to the wlan0 interface:
192.168.0.21/24 matches the IP found in /etc/pihole/setupVars.conf
[✓] IPv6 address(es) bound to the wlan0 interface:
2603:8000:ce03:4500:f4e9:66dc:61a7:d7e5 does not match the IP found in /etc/pihole/setupVars.conf (https://discourse.pi-hole.net/t/use-ipv6-ula-addresses-for-pi-hole/2127)
The IPv6 interface identifier for your Pi-hole's host machine has changed.
Also, you've configured Pi-hole for one of your host's public IPv6 addresses (GUA), where the IPv6 prefix is subject to be changed by your ISP also (either regularly or initiated by certain events like power-cycling your router).
If possible, configure your router to distribute an IPv6 ULA prefix as well, and Use IPv6 ULA addresses for Pi-hole.
Regardless whether you are using a GUA, ULA or link-local IPv6 address:
In either case, in order to make Pi-hole aware of a changed address, run
pihole -r
and choose Reconfigure.