If the tracking for Japan Post, FedEx, or DHL is invalid, it's likely that the carrier has not updated the tracking information yet, especially if you are checking the tracking immediately after the order has been shipped.
Please note, particularly for Japan Post, their tracking update service is either unavailable or severely limited during weekends. As a result, shipments sent with Japan Post on Friday afternoon or Saturday are typically available for tracking starting on Monday, usually in the afternoon Japan time.
If the issue persists, please feel free to open a support ticket and contact us.