I got that message until it showed up in the japanese system.

If I let the site autodetect the carrier and the destination country then I still get that message.

If I select the country of destination and let the site autodetect carrier then I get the tracking info (from the JP website).

I just checked on the Japan post (carrier at destination) website and I get the tracking details. I would try the destination

countries tracking website with the AP number as it also is the customs declaration number when you use registered post

I posted January 24