If you're encountering an error when trying to add a shared itinerary, it could be due to your access level as a collaborator. As a collaborator, you have limited editing rights on shared trips. When adding a shared itinerary, make sure you're in the correct tab. Toggle over to 'Shared with Me' to access itineraries that have been shared with you. If you're still unable to add the itinerary, it's possible that you don't have the necessary permissions. If the issue persists, it's best to reach out to the trip owner or your agency administrator to ensure you have the appropriate access level for adding shared itineraries. They may need to adjust your permissions or share the itinerary with you again.