A PayPal® issue regarding processing IPNs may impact some WHMCS users. Some IPNs originating between 18th September and 5th October 2023 are missing important data.

WHMCS may not record some PayPal payments during the impacted period.

Your PayPal account will receive payments but WHMCS will not record the transactions or update invoices to the Paid status. Additionally, you may see Invalid Receiver Email errors at Billing > Gateway Log.

To troubleshoot this issue:

1. Log in to your PayPal account and go to the IPN History page.
2. Click Message ID for the transactions that WHMCS did not record.
3. Copy the IPN Message section.
4. Go to PayPal Merchant Technical Support to report the issue to PayPal.
5. Paste the IPN message into Technical Support Identifiers.
6. Complete the other fields and click Submit.

PayPal Technical Support will investigate the incident and provide an update when they have resolved it.

To mitigate this issue:

1. Record transactions manually in WHMCS. When manually entering transactions, make certain that you enter the PayPal transaction IDs correctly to avoid later duplication when resending IPNs (below).

2. After PayPal resolves the incident, request that they send the failed IPNs again.

3. Migrate to the PayPal Checkout module. This newer module uses a different PayPal API which does not appear to be affected by the issue. For more information see PayPal Checkout Migration Guide.