Apple developers rejected my app with this reason.
"Business - 3.1.1 Your app includes an account registration feature, which is considered an access to external mechanisms for purchases or subscriptions to be used in the app. This feature does not comply with the App Store Review Guidelines.
Next Steps Please remove the account registration links and any other fully qualified links to your site that could indirectly provide access to these mechanisms, such as links to web pages for support, FAQ, product or program details, etc."
The users can use the app in demo mode (without registration) with some restrictions, but if they register they can use without registrations. The registration is not in webview. The client sends the user's datas to server.
Can someone help me?
You basically have two ways to solve the problem.
1) Sell the subscription etc. only through the App Store in the app (similar to Dropbox/Office etc.), i.e. there should be no links to your website, where your users have/can insert payment information. Look at the mentioned examples, how they solve this.
2) Only sell the subscription/services via the web, but never ever link to these pages via your app (similar to Kindle app, partially Spotify).
Your app must still be somehow (open for interpretation) functional for users without a subscription / registration.
The main issue Apple has, is that it's possible to circumvent the store and Apple's 30% cut. Just make sure that users are not able to purchase any digital products & services
Apps may not include buttons, external links, or other calls to action that direct customers to purchasing mechanisms other than IAP.
Source: https://developer.apple.com/app-store/review/guidelines/#payments