OK, got an answer from Zavvi UK, it was like pulling teeth, but here's the scoop.
Yes, it's a shipping issue:

Hello Jacques,

Thank you for getting in touch.

I apologize for the inconvenience.

Unfortunately, due to recent changes with our courier we can no longer ship to some countries including the USA which I do apologize for.

Sadly we don't have a confirmed date for when we will be shipping again, however this is continually being monitored and when possible we do hope to ship to here again.

Once again we apologize for the inconvenience caused.

If there is anything else that we can do, then please do not hesitate to get in touch and a member of our team will be happy to help.

Kind regards,

Slondiwe

Zavvi UK Customer Care Team