By visiting the Activity section of your event, you'll be able to see every person that has ever registered for this webinar:
You can search for an individual Registrant by name or email with the search box:
Once you find the person that you're searching for, just click on the name to see their full information:
Here, you can see the Registrant's Activity Log and Unique Join Link. You can Cancel Registration or Resend Confirmation in an email from here as well!
By clicking on Resend Confirmation the Registrant will receive another confirmation email with their Unique Join Link for the specified webinar.