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Expected Behaviour:
All devices to be shown on the Network Overview page and ads being blocked.
Actual Behaviour:
Only certain devices being shown on the Network Overview page, of which only one is using pi-hole. When browsing on my phone I can still see ads and it's not shown on the Network Overview page, other devices that are there are shown as "Device does not use Pi-hole".
Your debug log shows that Pi-Hole is properly processing received DNS requests. The problem is that the requests aren't getting to Pi-Hole. This would indicate a problem in router and/or client settings.
From a client you believe should be connected, what is the output of nslookup pi.hole?