My team recently found that registrants are not able to submit pending payments after an event is complete (the end date has passed). When the registrant clicks "Pay Pending Amount" in their confirmation email, it routes them to the event website with no payment option. Post-event, when an admin clicks "Edit Registration" for a registrant, they are routed to the event website and can see the "Pay Now" option. After extending the event date, the "Pay Now" option is visible to registrants.