After an Opt-in invitation is sent, the traveler has a choice to either Opt-in or Opt-out of messaging. If they have responded, you will see a "View Profile" link next to their email address in the View Itinerary page from the Agent Advantage console.
Clicking on that link will bring you to their Traveler Profile if they have decided to Opt-in. If they have decided to Opt-out, you will see a message that reads "This traveler has opted-out. To opt them in, fillout the user and traveler info."
Please see the following attachments: