I use this plugin with Codisto to supply to both eBay & Amazon. this has been going well until recently when Amazon have implemented a change to their tracking requirements and it's causing a bit of a problem.
They are now requesting that the shipping company, shipping service & tracking number are all provided. As well as this, it seems how the shipping company is pushed through they are now not accepting as a valid choice. I'm not sure if this issue would be down to this plugin or Codisto.
I've attached some images for reference.
RejectedTrackingInput.jpg shows how the tracking comes through to Amazon.
AmazonInputFields.jpg shows how Amazon is expecting the input, however I've been informed that the second text box can also be a drop down selection too depending on the company.
AcceptedTrackingInput.jpg is the shipping information that has been manually input into amazon.
I hope this information helps.