Why did I get API error code 10001?

Issue
PayPal presented API error code 10001.

Cause and Solution
This error can appear for many reasons. If you haven’t seen the API error codes page, it’s worth reviewing, but we’ll explain a few causes in this FAQ. Causes for this error code depend on the API you’re using, but you can understand why you got the error by looking at the short message and long message in the API response.  

Error Message Cause Solution
“ButtonSource value truncated” The value for the ButtonSource was cut off because it is too long.
For example, in the Express Checkout API, ButtonSource is
described as “Identification code for use by third-party applications
to identify transactions.”
Modify the ButtonSource value. It must be no more than
32 single-byte characters long and alphanumeric.
“Internal error” or “Transaction failed due to internal error” This is a generic error. For help resolving this issue or others, visit PayPal's
Contact Customer Service page. To help us fix the problem, give
us as much information as you can (such as time of the transaction,
the amount, and any error messages you received).
“Warning. an internal error has occurred. The transaction id
may not be correct.”
The transaction ID may have been changed or cut off from one
API call to the next.
For help resolving this issue or others, visit PayPal's
Contact Customer Service page. To help us fix the problem, give
us as much information as you can (such as time of the transaction,
the amount, and any error messages you received).
“The transaction failed as a result of invalid credit card number.
Check the number or attempt with another credit card.”
The card-issuing bank, not PayPal, rejected the transaction because
they consider it to be invalid.
Ask the customer to check with their bank. Neither PayPal nor the
merchant can discuss the issue due to privacy restrictions on
bank/customer interactions.
“Receiving Limit Exceeded” Accounts have transaction limits. For help resolving this issue or others, visit PayPal's
Contact Customer Service page. To help us fix the problem, give
us as much information as you can (such as time of the transaction,
the amount, and any error messages you received).
“Transaction refused because of an invalid argument. See
additional error messages for details.”
The MassPay RECEIVERTYPE wasn’t recognized. For help resolving this issue or others, visit PayPal's
Contact Customer Service page. To help us fix the problem, give
us as much information as you can (such as time of the transaction,
the amount, and any error messages you received).


For help resolving this issue or others, visit PayPal's Contact Customer Service page.