I built what Apple would describe as a "reader" app. Because it involves legal and financial information, however, it doesn't qualify as a standard "news" reader, so Apple is not treating as a reader app. That means it needs to have in-app subscriptions. Fine. I think that's a better UI choice for the user anyway.
The problem is that the App Store Connect UI for subscriptions and the training materials for Apple's reviewers on subscriptions are horrendous. As my other posts on these forums have documented, they literally do not work. Now with the app in the review process, the reviewers keep sending back rejections because they keep trying to sign up for a subscription with the provided demo account that is already signed up. Why is the demo account already signed up? Because it's a demo account! And that's what Apple wants (to test each and every feature)!
Fortunately, there are additional in-app subscription sandbox accounts I've provided credentials for so that from a clean slate, the reviewers can choose a plan and test signing up using those. But they apparently either don't understand that it makes no sense to sign up twice for a subscription or they refuse to do it without explaining why. Instead, they claim that there is some UI problem with the app because it won't let a signed-up account sign up again. This is bonkers.
The obvious solution is that if Apple wants each subscription to have a dedicated test sandbox account, then when you add a subscription plan, the credentials for such an account for the reviewers to use should be required fields. But they're not, and now I've wasted two weeks dealing with a feature that technically should not be required for the app at all by Apple's own guidelines.
Apple has been less than helpful when trying to sort this out. The entire process is hugely inefficient. If you could just set up a block of 10-20 minutes as an appointment to speak to your reviewer(s) instead of a round-robin that gets you a response once per day at best, it would eliminate probably 80% of the needless back-and-forth that the current process yields.