You're likely sending an order to a destination country using a currency that is not allowed for that country.
To resolve this issue, go to your Packeta client account and set the allowed currency for the destination country to match the currency of the order:
https://client.packeta.com/en/user-conversions/
This will ensure that the shipment is accepted even if the order is in a different currency.
Example:
If you're sending an order to Poland and the order is in EUR, ensure that your Packeta account is set to EUR for Poland.
