From where do you call the Redirect::away call in your controller. It sounds to me that you're doing this in your frontend. However, your frontend is not allowed to redirect you. Instead, you need to send the payment url to the frontend and replace the URL or open it in a new tab. A redirect won't work here.
redirect()->to($payment->getRedirectUrl()) should work as well ;) (At leas that is what I use with Mollie)