Why did I get API error code 10321?
PayPal returned API error code 10321 - Insufficient Funds when using Mass Payment.
Cause
Your PayPal account has insufficient funds to cover the total of the Mass Payment transactions plus PayPal's Mass Payment fees. If you're waiting for funds to clear from an eCheck, these funds aren't included when calculating available funds for the transaction.
Solution
Ensure that you have adequate funds in the PayPal account to cover the Mass Payment before making the API call.
See the Developer Portal for a complete list of NVP/SOAP API error codes.