Hello
Subdomains not working for specific ips although it is working for another in same location. There are other domains/subdomains working for the ips which dont work for the specific subdomain. Defining different subdomain also did not work. What could be the problem?
Pick one specific subdomain to troubleshoot. 
that DNS record, then make sure that subdomain is working as expected with HTTPS. Only then should you 
that record, and double-check your SSL/TLS setting to make sure it’s Full (Strict).
Thank you very much, it worked!
It is working for specific client but not all clients, we cleared caches also, what is next?
We cant set it as Full (strict) since there is no valid certidficate on the server side, subdomains are still inaccesible when re-enable proxy option.
it seems one of cloudflare ip block used to come over that specific domains and that ip block has been blocked by our firewall. thank you.