There is no $this->redirectUrl, should be $this->getRedirectUrl()

Author: maclof

src/Omnipay/Common/Message/AbstractResponse.php

@@ -100,7 +100,7 @@ public function redirect()
         </form>
     </body>
 </html>';
-            $output = sprintf($output, htmlspecialchars($this->redirectUrl, ENT_QUOTES, 'UTF-8'), $hiddenFields);
+            $output = sprintf($output, htmlspecialchars($this->getRedirectUrl(), ENT_QUOTES, 'UTF-8'), $hiddenFields);
 
             HttpResponse::create($output)->send();
             exit;