I recently moved our site to the Pantheon platform. The domain is the same (except the 'www' is now default where previously non-www was the default).
But we have just received this email from Paypal:
Please check your server that handles PayPal Instant Payment Notifications (IPN). Instant Payment Notifications sent to the following URL(s) are failing:
If you do not recognize this URL, you may be using a service provider that is using IPN on your behalf. Please contact your service provider with the above information. If this problem continues, IPNs may be disabled for your account.
Thank you for your prompt attention to this issue.
I tried accessing the address and got there without any trouble. Why might this be happening and how could it be fixed?