If you are using the Linkpoint API (or Firstdata) as your payment gateway, you might get an error that the connection was refused. The fix is very simple.

Make sure the port 1129 on your server is open both inbound and outbound. This is the port on which Linkpoint receives request for transactions.

To check if the port is open, you can run a curl command from the shell:

curl https://secure.linkpt.net:1129/

This should return at least some string. If this command return the message "curl: (7) couldn't connect to host" then your port is not opened.