We have been running IPN payments for around 15 months now, and for all that time we have around 10% missed IPN notification (there is no record of PayPal attempting to contact our website to notify it of the IPN, Paypal IPN history gets always http200.
Now we are hitting around 5 missed notification per 30 orders/day. We have tried to set up manually url listener in account settings and after that we are getting hundreds notifications from ebay sales) and also passing url method was used - nothing helped. Any idea how to diagnose the problem?
Thanks in advance
Although it is possible some situations don't trigger IPN, IPN actually covers a lot of things. I'd recommend getting in contact with paypal merchant technical services (or with paypal customer support, and they will transfer you to technical) as soon as possible, and ask them to see if there's anything wrong on either side. You would need to prepare the related transaction is within 28 days whose IPN is missing, because IPN only remains in the history for 28 days.