Has anyone ever been rejected by Amity University Noida?

Yes, one of my friends, who applied for one of the famous courses(BJMC) got rejected for Amity. But in the interview round she got a few answers wrong. Besides, she also had a gap of four years in her studies due to some medical issues.

The next day, she got informed through the website that she was not selected for her course in which she applied.

It is certainly not true that everyone gets admission in Amity very easily. A huge number of students apply to Amity University every year. So, it is evident that some of the applications will be rejected. 

Some people I know secured marks that, without even an interview, would get them admission anywhere, because CBSE is obviously not frugal with respect to giving marks. On the other hand, the NIOS is not typically very generous. Moreover, if you have experienced a huge gap in your studies, then that will be an issue too.