Paypal Ipn


I have been having an issue lately with Paypal payments, where the order stays in OPEN for a long time (sometimes over an hour) even though when we check Paypal, the payment was received instantly.

Sometimes the orders move to PAID instantly, but sometimes I have to move them manually.

Today I received an email from Paypal stating:

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.

Any ideas why the IPN's are failing?

The link ends with this: