Quick Tip: Solution to Paypal IPN Always Returning “Invalid”
When developing with PayPal’s IPN simulator, you might run into the situation where it keeps returning “Invalid” when verifying the message, regardless of the encoding you set or all conditions matching and being valid.
The Paypal developers team is notorious for ignoring all inquiries, and the docs are famously hard to read, so debugging these issues is incredibly hard and can cost you hours upon billable hours. I’ve even gone as far as set up a live server for testing the IPN simulator, for fear Ngrok was at fault when testing locally, and even added a certificate to the endpoint to get HTTPS going – no dice. In the end, the solution was – as is usually the case – simple but obscure.
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