Empty PayPal response.

An empty response typically means something is going wrong with the cURL request. You would need to add some troubleshooting in the code to view the exact error.

Are you sure you have cURL enabled on the server? If so, and you’re getting this with PayPal but nothing else, then it probably has something to do with the SSL protocol. You need to make sure your server supports TLS.

For more details on that check out this info about the POODLE vulnerability. PayPal and many other web service providers started blocking requests that weren’t using TLS.

Check into that and let me know if that helps. Sometimes the easiest thing is to ask your hosting provider if your server supports TLS so that it’s not vulnerable to the POODLE bug.