I'm getting the above error response when trying to use paypal express checkout. Below it the pertinent log file. I assume I am on an outdated version of the product but am at a loss as to how to upgrade (our company hired a third party who implemented zen, then they went under leaving me the task of trying to figure all this out).

https://api-3t.paypal.com/nvp
live
Request Headers: array (
0 => 'Content-Type: text/namevalue',
1 => 'X-VPS-Timeout: 45',
2 => 'X-VPS-VIT-Client-Type: PHP/cURL',
3 => 'X-VPS-VIT-Integration-Product: PHP::Zen Cart WPP-NVP',
4 => 'X-VPS-VIT-Integration-Version: 0.1',
)

Request Parameters: array (
'' => NULL,
)

Response: array (
'ACK' => 'Failure',
'L_ERRORCODE0' => '81002',
'L_SHORTMESSAGE0' => 'Unspecified Method',
'L_LONGMESSAGE0' => 'Method Specified is not Supported',
'L_SEVERITYCODE0' => 'Error',
)