The target replica is a data sender. Data senders can only import acknowledgment messages; they cannot import data change messages.
Ensure you are importing the correct message into the replica workspace. To ensure this, you could re-export an unacknowledged data change message from the relative replica using the Re-Export Unacknowledged Messages tool and subsequently import this message to the target replica. See Synchronizing disconnected replicas for more information. To determine if a replica is a data sender or a data receiver, see Managing replicas.