Failed to submit order to FBA (click for full log). Error Message:
Value UnexpectedValue for parameter PerUnitDeclaredValue is invalid. Reason: 1 error:
The field Per Unit Declared Value has a value of EUR, was expecting GBP
The reason for this error is that FBA received an order with a currency that did not match your Seller Central account's home region currency.
This scenario and others similar to it are exactly why we added the manual currency override feature / setting. If your account's home currency is GBP, you'll want to set this for GBP in the Override Currency setting under WooCommerce > Amazon Fulfillment, and figure out the best "middle road" conversion factor to use. The default value is 1. This will be used in the "declared value" field that FBA requires. The only other option is to make sure WooCommerce is configured to only handle payments in a single currency that matches your home region's primary currency.
In any case, WooCommerce (or NS FBA with the override setting enabled) must ALWAYS send the currency that Amazon is expecting since that is what your FBA account is based on. It's a hard restriction of FBA.