Amazon Payments- shipping amounts

Hi

Im using opencart 2.01 and want to use Amazon payments.

Everything is installed correctly and it works perfectly with free shipping and flat rate shipping.

However due to the fact I have different weight bands, and use couriers I need the weight based shipping to work

If weight based shipping is selected - the price isn't passed to amazon - I get errors saying

There are no shipping options to the selected address. Please select a different shipping address.

anyone experienced this and know a fix