App rejected because of Business Payments In-App purchase

The signup requirement is a payment. You are asking users to pay with their personal information, which will come back to you as cash. That is an alternate payment method and therefore isn't allowed.

Thanks for your response!
We're using signup option for most of the app and does not mention any In-App purchases for getting approval.
Seems its not the excat reason for rejection, please help us if you find some specific points

Not that it's necessarily the issue at the moment, but you will soon be required to offer Sign in with Apple as well as sign in with Facebook (unless your app falls under one of the exemptions).

https://developer.apple.com/app-store/review/guidelines/#sign-in-with-apple

All I know is what you have posted above. Apparently, one cannot use your app without providing one or more personally identifiable tracking identifiers. That is pretty clearly in opposition to Apple's stated goals for its products. You essentially have an in-app purchase, with personal information being the currency. Apple does not permit that currency. You can either give away the product for free or use approved Apple's approved methods for in-app purchase.

All apps are supposed to do something before requiring a log in. It doesn't have to be very much but it must be something. For example, you could explain in detail and with a demo what will happen once the user signs up.

You should also be aware of this guideline:

4.8 Sign in with Apple

Apps that exclusively use a third-party or social login service (such as Facebook Login, Google Sign-In, Sign in with Twitter, Sign In with LinkedIn, Login with Amazon, or WeChat Login) to set up or authenticate the user’s primary account with the app must also offer Sign in with Apple as an equivalent option. A user’s primary account is the account they establish with your app for the purposes of identifying themselves, signing in, and accessing your features and associated services.

Sounds like your appeal cleared up the IAP issue(s), and if review's concern is as simple as wanting that app to do more prior to logging in, that's one thing, but it might not be that simple - not knowing more about your app makes it difficult to suggest changes that may help your case.

The suggestion to also use Sign In with Apple may be the key, tho.

Also keep in mind ASRG's 4.2 Minimum Functionality "If your app is not particularly useful, unique, or “app-like,” it doesn’t belong on the App Store. If your App doesn’t provide some sort of lasting entertainment value, it may not be accepted."

If you do add content/features/functionality that works without logging in, you might want to take that opportunity to add something significant that can help get into the store. Don't just phone it in...

I'd be curious how you get on, so if you have time and can update this thread it would be helpful, thanks and Happy Holidays!

Good luck.

Ken