Pi Hole should be accepting and serving requests (and blocking ads when neccessary)
Actual Behaviour:
All DNS requests sent to the Pi are not responded to and devices fall back to the secondary DNS server provided.
Additionally, the PiHole web interface reports that no query has ever been made to the device despite the fact it was serving requests until about a week ago. No notable change has happened on the Pi.
Indeed, you Pi-hole hasn't processed a single DNS query yet:
*** [ DIAGNOSING ]: contents of /var/log
-rw-r--r-- 1 pihole pihole 12932 Jul 12 22:29 /var/log/pihole-FTL.log
-----tail of pihole-FTL.log------
Imported 0 queries from the long-term database
-> Total DNS queries: 0
-> Cached DNS queries: 0
-> Forwarded DNS queries: 0
-> Blocked DNS queries: 0
-> Unknown DNS queries: 0
-> Unique domains: 0
-> Unique clients: 0
-> Known forward destinations: 0
The two most common reasons for this observation are
a) you didn't configure your network / clients to make use of Pi-hole as DNS server at all (not likely for you)
b) something on your RPi is blocking access to port 53, usually a firewall
You may want to recheck Pi-hole's port prerequisites.
Sorry for the late reply, but it doesn't seem like those ports are being blocked and I have both set DHCP on my router to serve the IP address of my pi as the DNS server and manually set them on a couple of devices as well.
Very strange indeed
A reinstall did not solve the issue
You have a connectivity problem. The Pi-hole IP does not appear to be reachable on port 53. This likely explains why no clients can connect to the Pi-hole for DNS resolution.
*** [ DIAGNOSING ]: Name resolution (IPv4) using a random blocked domain and a known ad-serving domain
[✓] secure.ace.advertising.com is 0.0.0.0 via localhost (127.0.0.1)
[✗] Failed to resolve secure.ace.advertising.com via Pi-hole (192.168.1.3)
You also appear to have recently reset the time on this Pi? This error shows a mismatch between the time in the Pi-hole logs and system time.
rw-r--r-- 1 pihole pihole 92 Jul 17 21:50 /var/log/pihole-FTL.log
-----head of pihole-FTL.log------
[2020-07-17 21:50:56.540 705] WARN: getOverTimeID(1595019300): 557 is too large: 1594685100
I suggest to use another sd card, do a quick install of your rpi and install pihole to see if it works. (it should)
Then either do a search of what setting is causing the mishap or do a clean install on that new sd card.
I personally have adopted the habit to reinstall instead of searching. It saves me a lot of time and nuisance.