While setting up an IPN installation I came across some problems using the IPN developer tools. Which lead me to information to suggest that the IPN emulator only now works on SSL and that the live IPN will not support http:// PayPal IPN ONLY works over SSL.
IPN Verification Postback To HTTPS
If you are using PayPal’s Instant Payment Notification (IPN) service, you will need to ensure that HTTPS is used when posting the message back to PayPal for verification. After June of 2017 HTTP postbacks will no longer be supported.
How does this affect you?
If you use PayPal on your site for taking payments, then you may be using IPN. IPN is a way for Paypal to tell your site when a payment has been approved or cancelled. It has been the common way to ‘talk’ to PayPal for some years.
If your PayPal IPN stops working then you will not get orders updated with payment confirmations. I have seen some site owners who use the PayPal email for reference and don’t even check the WordPress Dashboard!
You really should be taking advantage fo the SSL offers from most hosting companies if you are taking orders on your site, even if you do not take the card details yourself, (when you send them to PayPal). People are being educated to expect SSL sites with https:// These are more secure and orders pages are then encrypted.
So if you are not already SSL site, then contact your developer or hosting company and get upgraded.
The simple takeaway is that if you take orders on your site, even without payment, the world is expecting your site to be https://