Should be available according to the status updates: https://www.x.com/content/completed-oct-19-maintenance-pp-live-2837

The service interruption to IPNs (Instant Payment Notifications) ended at Oct 19, 11:58 PM PDT and interruption to MassPay ended at Oct 20, 12:06 AM PDT. Both services are now available, however the maintenance activity is still in progress and the maintenance window will be open until Oct 20, 1:00 AM PDT (Oct 20, 9:00 AM BST)