Hiya, so I solved the issue it was the MWS Secret key…After replacing it, the issue went away…although I would have expected the error to be related to that rather than the form variation issues.
Are you integrating Aelia Multi Currency into the compatibility for Amazon Pay…Aelia is a pretty popular multicurrency add-on, and is currently the one we are using. https://aelia.co/shop/currency-switcher-woocommerce/?utm_source=AdWords&utm_medium=Search&utm_campaign=MC-Plugin&gclid=EAIaIQobChMI7qP2tfiJ7AIV0-ntCh2RiA1DEAAYASAAEgLwv_D_BwE
I can see the scripts in your plugin for multi currency is relatively small, so hopefully not too much work to integrate. I could share access to my install if that would help so you can get the relevant hooks/variables (happy to contribute financially too).
