Unfortunately, this is a fairly common problem with the Google Play Store, whose payment validation process may fail if the bank has not done what is needed. It can also come from the connection with the banks' servers.
The payment is handled by Google, not by NavimetriX: the only options we can suggest are to:
- try again;
- try with another bank card;
- use a Google Play gift card, sold in supermarkets and many shops;
- take out the subscription on an Apple device (iPhone, iPad or Mac). Then create your NavimetriX account on that Apple device, right after subscribing, and log in to that account on your Android device: the subscription will be recognised there. See How to subscribe and create a NavimetriX account?