The short version is the tracker quit working, more than once. They thought they could update the tracking manually if that happened, but turns out it was too much work (ha! Welcome to the world of international shipping!)
Here is some of their long explanation.
As you know we've had some persistent problems with the tracking of the container which have been frustrating for many of you and for which I'd like to apologise.
"We attached a tracking device to the container at the start of the project [an Inmarsat C transceiver kit for those keen to know the technical details].
"Unfortunately the device developed intermittent problems, so when the container arrived in New Jersey late last year we removed the device and it was returned to the UK for repair before being shipped back to Brazil and re-attached to the Box.
It worked for a while but now we have lost the signal again. As part of our planning for this project we had a system in place to switch to the appropriate individual ship's tracking devices in the event of such a fault.
Whilst that has been possible it has required greater resources than we have available to manually carry out this process over such a long period. Our contingency planning allowed only for short periods of a faulty transceiver and not the seemingly intractable problems we have encountered.
But, at least they attempt to give us an idea of the future track of this container.
They say it will go to Russia, so I can only guess that the some of the cargo will be removed in Japan and the box will continue onward. If this is correct then the shipper on the ocean bill of lading is probably a freight forwarder, or consolidator (some thing, different names).
Here's what the BBC has to say, without committing to a time line.
The Box is currently in Hong Kong en route to Japan. From there we expect it to travel to Russia before a final return to the UK in June/July. We hope to bring television, radio and online reports from each of those locations and we will attempt to manually update the position as frequently as we are able.