Ok...so from FCOM:
When the circle intercepts the current flight path, the FMGS compute the time, the along path distance and the altitude at the first intersection point, from the current aircraft position (small green font).
A large blue star is then displayed to insert the intersection waypoint into the flight plan.....etc
Based on the above i can only imagine the airport inserted was not the corrrect one ? or maybe the flight plan was not completed thus not intercepting the circle ?