Paypal Pro Error 10552 Invalid Configuration

[riomaha]

I am running Z.C 1.5.7 (not A,B, or C) with PHP 1.7.2. The PayPal module was not altered (stock)
I initially set it up using old Paypal method but noticed that they are pushing for Clous Sandbox. So I created a sandbox account and generated an API, Username, Signature, etc.

In my ZenCart setup, I enabled both Express and Pro payment module and update the settings accordingly. Unfortunately, each time I try to checkout, I get an error 10552 Invalid Configuration. So I double checked my settings in ZenCart and PayPal and also checked the files. I noticed that 1.5.7C has slight changes to Paypal Pro so I updated the Paypal Payment module with the new files but still get the same error



I understand the module requires Curl which is indeed enabled on my server but I have to use a proxy server. So I tried by updated PayPal Curl file to include the Proxy server as below and still no luck.

    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $this->_endpoints[$this->_server]);
                                curl_setopt($ch, CURLOPT_VERBOSE, 1);
                                curl_setopt ($ch, CURLOPT_PROXYTYPE, CURLPROXY_HTTP);
                                curl_setopt ($ch, CURLOPT_PROXY,"http://proxyserver.domain:port");
    curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $this->_buildNameValueList($values));
    foreach ($this->_curlOptions as $name => $value) {
      curl_setopt($ch, $name, $value);
    }

I viewed the log files with and without proxy and they are identical.

Response: 
Array
(
    [TIMESTAMP] => 2021-08-04T15:36:06Z
    [CORRELATIONID] => 41eaad0664e08
    [ACK] => Failure
    [VERSION] => 124.0
    [BUILD] => 55025969
    [L_ERRORCODE0] => 10552
    [L_SHORTMESSAGE0] => Invalid Configuration
    [L_LONGMESSAGE0] => This transaction cannot be processed.
    [L_SEVERITYCODE0] => Error
    [AMT] => 1.00
    [CURRENCYCODE] => CAD
    [CURL_ERRORS] => 
)

Any thoughts?