Flutter: "unable to find the following required information in your app's binary"

I got this from App Store review:

We noticed that your app did not meet all the terms and conditions for auto-renewing subscriptions, as specified in Schedule 2, section 3.8(b) of the Paid Applications agreement.

We were unable to find the following required information in your app's binary:

– Length of subscription (time period and content or services provided during each subscription period)

I use Flutter to build my iOS app. Could that be why Apple can't find the information in my binary?