I had a game with an ad that comes up at startup like I've always done. Apple rejected it today. We noticed that your app requires customers to view advertisements prior to using it, which is inconsistent with the recommendations in the Apple iOS Human Interface Guidelines. As stated in the Apple iOS Human Interface Guidelines: "People use your application to get things done or to be entertained; they don’t want to feel as if they’re being forced to watch an advertisement". "In iOS 4.0 and later, you can allow advertisements to display within your application and you can receive revenue when users see or interact with them. It’s essential that you plan when and how to integrate ads with your UI so that people are motivated to view them without being distracted from your application". Next Steps Please remove the forced advertising and resubmit your app for review. If you wish to deliver ads to your users, consider offering passive advertising; paying customers typically expect advertising-free content.
This happens from time to time been going on for years now. Your solution is best, the other option is to upload with no ads but don't release. Then turn ads on when you submit an update, then release. Usually that will work as well.
Yes - it was an interstitial that came up when opening the game. I submitted a new binary and went to my Chartboost dashboard and turned off the campaigns.