Unfortunately, this is a relatively frequent problem with the Google Play Store, where payment validation processes can fail if the bank has not taken the necessary steps. But it can also be due to connection problems with bank servers.
We have no other procedure to suggest than:
- install the app
- try to pay with a bank card
- use a prepaid card for the Google Play Store, available from supermarkets or tobacconists
- find someone you know an Apple device’s owner with which this type of malfunction almost never occurs.