Same here, did you fix that?

var_dump the session_id, to know if it's the same session id used when you save and when you fetch datas.

    public function getApiInfos() {
      return array(
        'cancelUrl' => \URL::route('pages.payment.canceled'),
        'returnUrl' => \URL::route('pages.payment.success'),
        'amount' => Session::get('amount').'.00',
        'currency' => 'EUR'
      );
    }

I'm using same method on redirecting and fetching...

I don't know why, it's working now on Firefox but not on Chrome.. I still get "[L_LONGMESSAGE0] => This transaction cannot be processed. The amount to be charged is zero." this error...