This is a message from a fraud detection system Google uses to prevent malicious payment transactions from being executed. Before executing a payment transaction, Google will analyse how safe a transaction is. Multiple parameters can impact this check.
Google may identify a payment as a "bad transaction", when multiple payments from different devices are made using the same credit card, or when the same credit card is used by multiple accounts, or when the user pays and then cancels payment multiple times in a row, etc.
If you are experiencing payment issues with Google, please contact Google Play Support;
You can refer to this article if you want a basic run down on how to properly contact Play Store Support; https://www.gumisupport.com/hc/en-us/articles/202460406-How-do-I-contact-Google-Play-Store-Support-