Hi @TaniaH ,
Thanks for joining us in the Community! If your event was completed, you are not able to edit the event links, register someone manually or update the event date. What you can do is to add these additional registrants to the spreadsheet that you are able to generate from the reporting tab of the event. For more information on this tab please click here.
I apologize for any inconvenience this workaround may cause. However at this time we are only fixing critical issues on our events program. Though we are not planning any further development at this time, I have tracked your experience in the event that there is any change in the future.