Users are
registering for our event
and paying by Paypal, but they show up in the system as Pending and must be manually set to Paid via the admin. What is the cause of this?
That usually happens because PayPal IPN Messages could not reach your site for some reasons, so Events Booking does not know about payment to update status of the registration record
For this, please submit a support ticket so that I can guide you to check it further