To set up a Zap that triggers from PayPal, you need to add the webhook provide by the Zap's trigger action in PayPal's Instant Payment Notification (IPN) section. You can learn more about the IPN settings in PayPal in this help doc from PayPal.
Many users are already using the IPN for another purpose, like managing ecommerce software, and so can't use it for Zapier.
Is this something that folks have come across and do you have any suggestions for workarounds?