Why did I get API error code 10426?
We return this NVP/SOAP API error code when the transaction is refused due to an invalid argument with the ItemTotal, and the amount is invalid.
Review the amount entered. Payments cannot contain more than two decimal places. You can try to resolve the error by number-formatting the amount in the coding language used and limiting the decimal places to two or fewer digits.
See the Developer Portal for a complete list of NVP/SOAP API error codes.