If you have IPN enabled and receive payments from different sources (eBay, Magento and others) to the same PayPal account, PayPal unfortunately continues to try sending notifications related to these order to the Magento store, where these orders don't exist.
A possible solution is to create a centralized IPN receiver, please refer to this page for a very useful script to get you started.
Hope this can help you! Let me know if you need further assistance.
If issue solve, Click Kudos & Accept as Solution.
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