The system will not let you enter someone with the same name and birthdate twice to avoid duplicate entries for an attendee. If the system is not letting you enter somebody, there should be a warning note just about the submit button.
NOTE: If you are entering many entries, and just one of those is a duplicate, you will not be able to process them. We recommend that you arrange your browser so that you can see the submit button. As soon as you enter a duplicate, the error will appear.
If you can not enter an attendee, it means that it is already in the system. If it does not appear on your roster, it will be in one of two places.