Thanks for jumping in! All the messages are like: Access Denied You don't have permission to access "http://www.paypal.com/cgi-bin/webscr" on this server. Reference #18.77171602.1496070447.16ce2427 The Reference number changes from call to call but it always starts with 18. Although the message mentions "http://www.paypal.com..." the POST is sent to "https://..." The IP of the merchant site is 82.223.249.123. However, the actual POST requests to PayPal are sent from each customers 'IP. Most of my trials are from 213.27.238.102, but the rest of my team have been testing from other environments. But the call fails from any IP we've tried (among many others, and those of our customers): - 83.48.63.17, - 176.82.37.36, - 188.172.194.164 - ... We've tried Chrome, Firefox, Explorer 11, Edge, from Widows 7 (32), Windows 7 (64), Windows 10. We've also tried from iPhones, iPads and various Android environments... Please note that the online shop at the ISBN Agency has been operating for over a year with no problems. It all started on April 7th night. No code changes involved... We don't have any scripts that might be sending (or that has sent) a large number of requests. The average transactions / month is around 150.
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