The Account Management System recognizes that the InForm Booking ID is associated with the former Associate and will only allow you to update a Client to Active Booked with a Booking ID that is yours.
In this case, the Client should be updated to the Prospect status if a search is not yet in progress, or the Active status if a search is underway. This Client can then be advanced to the Active Booked status once a new booking (under you) takes place.