What can be causes of the error: Curl Error: 28 - Connection timed out after 100001 milliseconds ?
This error in my case was happening when an PHP script (WHMCS HyperVM module) was trying to query remote server on this URL:


http://RemoteServerIP:8888/webcomman...vmipaddress_a=

What i tried is to disable mod security, whitelist IP in cloudflare which was used by the domain, whitelist both servers IPs in firewall.

What worked is to unblock RemoteServerIP (in my case HyperVM server) in frewall of the server which was sending the request (the WHMCS hosting server).

Maybe try to add remote server IP to the whitelist or ignore list too.

-----

I could verify that this error is returned only when i send request from that particular server. When i open above mentioned URL in my web browser, it works, i get no timeout. So this way i can manually execute timeouted URLs in my browser.