How to attach an IAP to my app review?

My app offers a premium subscription, and all works well locally when I test with a Sandbox tester account. However, in app review, the reviewers are not able to access premium - Apple does not open the subcription/payments modal when the reviewers click the "Get Premium" button.

I'm wondering if it's because I haven't "attached" my subscription to my review as described in https://developer.apple.com/help/app-store-connect/manage-submissions-to-app-review/submit-for-review/? The instructions says: "On the right, scroll down to the In-App Purchases and Subscriptions section, then click Select in-app purchases and subscriptions. When submitting a subscription for the first time, it must be submitted with a new app version."

But I don't see any "In-App Purchases and Subscriptions" section on this page. Am I missing something or are the docs outdated?