Why did I get API error code 10747?

It is required as part of the DirectPayment API request to pass the variable, IPADDRESS, when you capture the buyer's IP address from their browser.

Length constraints are 45 single-byte characters, including periods and colons. Check the IP address and make sure it is in the correct format: 

• IPv4 example, 255.255.255.255
• IPv6 example, FDEC:0:0:0:0:BBFF:0:FFFF or zero-compressed, FDEC::BBFF:0:FFFF
• IPv4-mapped IPv6 example, 0000:0000:0000:0000:0000:FFFF:255.255.255.25 or zero compressed, : :FFFF:255.255.255.25

PayPal highly recommends passing the buyer's IP address to detect possible fraud. 

See the Developer Portal for a complete list of NVP/SOAP API error codes.