UPDATE: PayPal has reported the issue is clear now:
This issue had been resolved as of Wed, 12 Feb 2020 16:30 GMT
PayPal is currently experiencing issues with Instant Payment Notifications today -- these are the notices we rely on to process orders after payment. We won't be able to process these orders until PayPal clears the issue up on their end, at which time our system will be able send out emails to update all of the affected buyers:
Initial Notification : Impact to Instant Payment Notifications (PP-LIVE-13006)
Incident Start: Feb 12, 12:00 UTCIncident End: On-going
Affected Regions: TBD
We are experiencing a system issue which may be affecting Instant Payment Notifications (IPN) on the Production environment. Merchants may be encountering HTTP 500 responses when sending IPN post backs to https://ipnpb.paypal.com/cgi-bin/webscr
Our technical teams are actively working towards resolving the issue.