Twilio cannot establish a TCP connection to your web server. The two attempts to connect to your web server were timed out. Each connection attempt has a 5 second timeout.
Possible Causes
firewall in your network blocking incoming TCP traffic
network outage between Twilio and your web server
invalid host part in the HTTP URL pointing to non-existing host or private IP address
Possible Solutions
verify firewall configuration in your network or on the web server
verify network connectivity to your web server
verify the HTTP URL provided is accessible to the public Internet