It`s possible to resend an IPN transmission, which can be useful if your website went down at the time Paypal sent the callback response. To resend
a IPN message do the following:
[1] Log into your
Paypal account.
[2] From the left menu, select 'Selling Tools > Seller Preferences'.
[3] From the next screen, select 'Getting paid and managing risk > Instant payment notifications > Update'.
[4] Click the '
IPN history page' link.
[5] Select the transmissions you want to resend and click 'Resend Selected'.
Done.