Why did I get result code 29?

PayPal presented result code 29 - Expected comment or processing instruction. (You may also receive the text "Invalid XML stream: Invalid XML document.")

There is a known issue with submitting XML transactions using Version 3.06 of the Payflow Pro COM client.

To resolve this issue, uninstall Version 3.06 and install the latest client available in the Downloads section of PayPal Manager

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