SimpleSAMLphp response not handled

Question

Have set up a SimpleSAMLphp configuration with correct metadata and login details. We can successfully login to the idp , and we can see responses back from the provider that show the detailed SAML response for the user. We are using the Chrome SAML-Tracer plugin, and we see all the assertions and account information for the user in the response, but the simple PHP test page below is stuck in a loop.

<?php
require_once ('../../simplesamlphp/lib/_autoload.php');

$saml_auth = new SimpleSAML_Auth_Simple('default-sp');
if ($saml_auth->isAuthenticated()) {
    $attributes = $saml_auth->getAttributes();   
    var_dump($attributes);    
} else {
    $saml_auth->requireAuth();
}

Loops forever as the isAuthenticated is always false .... keeps trying to log in again , but provider returns SAML response over and over. Any suggestions as to what is going wrong ? Ubuntu 20.04 , SimpleSAMLPHP v1.19

changed the metadata and config files, no luck