PHP Stripe save for future use not showing UI

First of all I am working from this URL
https://docs.stripe.com/payments/save-and-reuse
I have watched the video on the page. In the video, after clicking the setup button. The Stripe UI comes up. I never get that screen and I have tried different browsers.
The customer is created. The event log shows.

 A new SetupIntent seti_1Ol4kvGznLM7Qekn5jObbbLm was created

The log screen shows a 200 OK POST /v1/checkout/sessions. But the UI never comes up. What am I missing?

 require_once "vendor/autoload.php";

 // Set your secret key. Remember to switch to your live secret key in production.
 // See your keys here: https://dashboard.stripe.com/apikeys
 $stripe = new StripeStripeClient('sk_test_51J5VXM');

 $customer = $stripe->customers->create([
    'description' => 'HealthScribe Client',
    'email' => '[email protected]',
    'name' => 'Jenny Rosen2',
 ]);

 $stripe->checkout->sessions->create([
    'mode' => 'setup',
    'payment_method_types' => ['card'],
    'success_url' => 'https://api.affordablecustomehr.com/stripe/success/?session_id={CHECKOUT_SESSION_ID}',
    'cancel_url' => 'https://api.affordablecustomehr.com/stripe/cancel',
    'customer' => $customer['id']
 ]);