In some cases RemNote will not be able to bill your credit card, preventing you from buying the Pro subscription.
Try these steps:
Confirm with your bank that your credit card supports foreign and online payment.
Try using another credit card. For other payment options, see How can I pay?.
If you don’t have another credit card, you can also consider using a prepaid debit card. You can likely find such cards in a local convenience store.
If none of these work, contact support and we'll sort it out.