Eu dei uma olhada na FAQ, mas tudo o que fiz n?o resolveu.
Testei pela sandbox e o log retornou isso:
>?POST?/wc-api/WC_PagSeguro_Gateway/?HTTP/1.1
>?User-Agent:?Jakarta?Commons-HttpClient/3.1
>?Host:?redatoronline.net
>?Proxy-Connection:?Keep-Alive
>?Content-Length:?85
>?Content-Type:?application/x-www-form-urlencoded
<?HTTP/1.1?500?Internal?Server?Error
<?Date:?Sat,?25?Jul?2015?12:52:58?GMT
<?Server:?Apache?Phusion_Passenger/4.0.10?mod_bwlimited/1.4?mod_fcgid/2.3.9
<?X-Powered-By:?PHP/5.4.43
<?Expires:?Wed,?11?Jan?1984?05:00:00?GMT
<?Cache-Control:?no-cache,?must-revalidate,?max-age=0
<?Pragma:?no-cache
<?Vary:?Accept-Encoding,User-Agent
<?Content-Type:?text/html;?charset=utf-8
<?Via:?1.1?pagseguro.proxy.srv.intranet
<?Connection:?close
<?Transfer-Encoding:?chunked
<?<!DOCTYPE?html>
<?<!--?Ticket?#11289,?IE?bug?fix:?always?pad?the?error?page?with?enough?characters?such?that?it?is?greater?than?512?bytes,?even?after?gzip?compression?abcdefghijklmnopqrstuvwxyz1234567890aabbccddeeffgghhiijjkkllmmnnooppqqrrssttuuvvwwxxyyzz11223344556677889900abacbcbdcdcededfefegfgfhghgihihjijikjkjlklkmlmlnmnmononpopoqpqprqrqsrsrtstsubcbcdcdedefefgfabcadefbghicjkldmnoepqrfstugvwxhyz1i234j567k890laabmbccnddeoeffpgghqhiirjjksklltmmnunoovppqwqrrxsstytuuzvvw0wxx1yyz2z113223434455666777889890091abc2def3ghi4jkl5mno6pqr7stu8vwx9yz11aab2bcc3dd4ee5ff6gg7hh8ii9j0jk1kl2lmm3nnoo4p5pq6qrr7ss8tt9uuvv0wwx1x2yyzz13aba4cbcb5dcdc6dedfef8egf9gfh0ghg1ihi2hji3jik4jkj5lkl6kml7mln8mnm9ono
<?-->
<?<html?xmlns="https://www.w3.org/1999/xhtml"?lang="pt-BR">
<?<head>
<? <meta?http-equiv="Content-Type"?content="text/html;?charset=utf-8"?/>
<? <title>Erro???WordPress</title>
<? <style?type="text/css">
<? html?{
<? background:?#f1f1f1;
<? }
<? body?{
<? background:?#fff;
<? color:?#444;
<? font-family:?"Open?Sans",?sans-serif;
<? margin:?2em?auto;
<? padding:?1em?2em;
<? max-width:?700px;
<? -webkit-box-shadow:?0?1px?3px?rgba(0,0,0,0.13);
<? box-shadow:?0?1px?3px?rgba(0,0,0,0.13);
<? }
<? h1?{
<? border-bottom:?1px?solid?#dadada;
<? clear:?both;
<? color:?#666;
<? font:?24px?"Open?Sans",?sans-serif;
<? margin:?30px?0?0?0;
<? padding:?0;
<? padding-bottom:?7px;
<? }
<? #error-page?{
<? margin-top:?50px;
<? }
<? #error-page?p?{
<? font-size:?14px;
<? line-height:?1.5;
<? margin:?25px?0?20px;
<? }
<? #error-page?code?{
<? font-family:?Consolas,?Monaco,?monospace;
<? }
<? ul?li?{
<? margin-bottom:?10px;
<? font-size:?14px?;
<? }
<? a?{
<? color:?#21759B;
<? text-decoration:?none;
<? }
<? a:hover?{
<? color:?#D54E21;
<? }
<? .button?{
<? background:?#f7f7f7;
<? border:?1px?solid?#cccccc;
<? color:?#555;
<? display:?inline-block;
<? text-decoration:?none;
<? font-size:?13px;
<? line-height:?26px;
<? height:?28px;
<? margin:?0;
<? padding:?0?10px?1px;
<? cursor:?pointer;
<? -webkit-border-radius:?3px;
<? -webkit-appearance:?none;
<? border-radius:?3px;
<? white-space:?nowrap;
<? -webkit-box-sizing:?border-box;
<? -moz-box-sizing:????border-box;
<? box-sizing:?????????border-box;
<?
<? -webkit-box-shadow:?inset?0?1px?0?#fff,?0?1px?0?rgba(0,0,0,.08);
<? box-shadow:?inset?0?1px?0?#fff,?0?1px?0?rgba(0,0,0,.08);
<? ? vertical-align:?top;
<? }
<?
<? .button.button-large?{
<? height:?29px;
<? line-height:?28px;
<? padding:?0?12px;
<? }
<?
<? .button:hover,
<? .button:focus?{
<? background:?#fafafa;
<? border-color:?#999;
<? color:?#222;
<? }
<?
<? .button:focus??{
<? -webkit-box-shadow:?1px?1px?1px?rgba(0,0,0,.2);
<? box-shadow:?1px?1px?1px?rgba(0,0,0,.2);
<? }
<?
<? .button:active?{
<? background:?#eee;
<? border-color:?#999;
<? color:?#333;
<? -webkit-box-shadow:?inset?0?2px?5px?-3px?rgba(?0,?0,?0,?0.5?);
<? ? box-shadow:?inset?0?2px?5px?-3px?rgba(?0,?0,?0,?0.5?);
<? }
<?
<? </style>
<?</head>
<?<body?id="error-page">
<? <p>PagSeguro?falha?do?pedido</p></body>
<?</html>
