400 Error when setting up the currency ( PLN) for eCommerce

Using Drupal Commerce Version: 7.x-1.13 Mailchimp Version: 7.x-4.5, MailChimp ecommerce 7.x-1.0

Problem:
When setting up the store with eCommerce and choosing Integration with Drupal Commerce + setting default currency PLN (code 985) or PLN from the the list below, I am getting this error:

400: Invalid Resource - The provided code 'PLN' is not a valid ISO 4217 currency code.

On the checkout form/cart on the store, the error repeats.

I check the currency-codes-iso4217.xml file and all is fine with the code number etc

I could synchronise the store with the list on the mailchimp account with EURO currency but now no data is available on mailchimp when trying to use Recommended products or Abandoned cart features though this functions are available for on mail chimp account for this synchronised list.

The support from MailChimp directed me here suggesting that you could help to solve this problem or tell me what to do :)

Any help solving this would be much aprocieted