I did my best? I tried to provide you with the screen shot replicating my earlier experience - it worked this time. Everything I’ve said is as truthful and accurate as I can be.
The visitor was seeing the JS challenge screen.
Neither his IP address or ISP ASN were under any rules.
Neither were logged in the firewall overview so the JS challenge wasn’t flagged.
I checked his IP address on my server and the forum software we run - no problems.
I tried to whitelist his IP address in CloudFlare - it made no difference.
I tried to whitelist his ISP’s ASN - this time it said ASN not recognised (not that it clashed with a previous rule, I hasten to add).
I tried to recreate this just now but this time it has worked (several hours since it didn’t work).
I’ve emailed the visitor to let me know if he’s still seeing the JS challenge - not received a reply yet.