If the scanned badge is not recognized, it is probably because the participant's profile is not well attached to his badge. Feel free to contact a member of the organization to have the problem fixed.
Here are some tips to get around the problem:
Take a picture of the badge. This will allow you to scan it later and save the contact profile.
Search the person's name in the list of participants to send him/her a connection request and, if you wish, a personalized message.
If the problem persists, please contact us at firstname.lastname@example.org so that we can help you.