I haven't confirmed this with PayPal yet, but it appears that PayPal is having issues on their end with sending PayPal IPN Data for transactions.

The issue appears to have started on 26 March 2007 at around 3pm. Since then, no callbacks have been being made.

This will affect all paypal invoice and subscription payments through WHMCS and any other systems using PayPal IPN so I'm sure it will be resolved quickly. It is also affecting our license order system and causing PayPal orders and invoice payments to need manually marking paid so there will be delays with these at the current time.

Matt