The problem is not where Obama was born. The problem is not his birth certificate.
The real problem is that he was born to a British citizen (his father)and as such cannot be a "natural born citizen" of the United States. He was, in fact, a dual American/British citizen until age 18 (his own website and the fact-checking website it referenced both state these very facts).
Why was this ignored? It was not hidden and, indeed, was admitted by Obama.