1) Create a blank page and put this code on it. That will tell you if there is anything wrong with the server itself
<?php
$ch = curl_init('https://www.howsmyssl.com/a/check');
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
curl_setopt($ch, CURLOPT_USERAGENT, $_SERVER['HTTP_USER_AGENT']);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
$data = curl_exec($ch);
curl_close($ch);
die($data);
$json = json_decode($data);
echo $json->tls_version;
?>
2) Dump the session on the failure page. That will tell you what the actual error is with this code:
<?php
@session_start();
var_dump($_SESSION);
?>
You can post back here with the result if you need help interpreting what you see.