Most probably this error happened because you have sent a payment method within your sent request payload (e.g. Apple Pay) that doesn't have been configured in your profile.
In this article you will be going to know about:
How to investigate the reason that caused this error?
You can investigate the reason for such an error from the "API debug log" by navigating to the Developers > Testing > API Debug Logs (within your desired profile).
Or you may get the error directly from the response payload received according to your sent request.
Reason #1: Not configured payment method.
This means that the payment method you are trying to pass in the request is not configured in your profile. In this case, whether you have to change the payment method to one of the configured ones already in your profile, or you will need to send an email to ([email protected]) with your profile id along with the country name that your business operates in, requesting this payment method to be added to your profile.
For more information about payment methods, you may like to check our "How to control the payment-method on payment page?" solution article.