The message "address unavailable" generally means that a location service (such as Find My iPhone or Find My Friends) has detected the device's location but is unable to pinpoint or display a specific street address or exact location details. This usually happens because the exact address data is not accessible or the location is not precise enough to be linked to a known address in the map database. Common causes include weak GPS signal, poor network connection, privacy settings, or the device being offline or powered off. It does not necessarily mean the device is lost, just that the system cannot provide a detailed address at that time.