Laravel | Redirect Does Not Change URL

Question

I am using an API from a payments-provider.

At some point, I show the user a page where he can authenticate himself (enter a code that the payment-provider will send him). Note that on this page, I render a div element that the payment-provider has given me through an API request I made previously (I used Guzzle for this).

After the user enters the code and clicks submit, the payment-provider redirects him to one of my pages - let's say /redirect. So, in my web.php I have a route:

Route::post('/redirect', 'OrdersController@redirect');

In my OrdersController I do this:

// do various stuff like updating the order status

return redirect("orders/$order->id");

There is another route in web.php:

Route::get('/orders/{order}', 'OrdersController@show');

And here is the show method:

return view('orders/show', [
    'order' => $order,
    'page_title' => 'Order Receipt',
]);

Two things go wrong:

1. The user gets shown the orders/show view but it seems like it is in an iframe:

2. The URL of the page does not change. It does not show myapp.test/orders/435 for example. Instead, it still shows the URL of the previous page (the one where the user authenticated himself) - something like myapp.test/authenticate let's say.

Any ideas why this is happening?

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Update with screenshot: