Establishing where a fault lies.
THE QUICKEST TEST
Pause Cloudflare from the dashboard. Traffic then goes directly to us, with the configuration left in place.
If the problem disappears, Cloudflare is involved. If it persists, it is not.
Unpause afterwards.
THE ALTERNATIVE
Set the relevant record to DNS only temporarily, which achieves the same for that hostname.
CHECKING WHAT CLOUDFLARE SEES
The security events log shows blocked and challenged requests.
The analytics show cache behaviour and errors.
CHECKING WHAT WE SEE
cPanel > Metrics > Errors, and Raw Access logs.
If we logged no error at the time, the request may never have reached us.
THE PATTERN
An error page branded by Cloudflare means Cloudflare produced it.
A plain server error page means we did.
That distinction tells you immediately which side to investigate.
WHAT TO CHECK IN ORDER
SSL mode Proxy states on records Optimisation features Firewall rules and security level