Didn't Nostradamus reject the word "prophet" and prefer "seer?"
1999 is awfully close to 2001. "From the sky a great king of terror" that allows "mars [war] to reign" sounds a lot like 9/11.
1 wrong prediction means they are not a prophet of the true and living God. But I do believe some people have extrasensory abilities within themselves, and dispensation of those fruits is still filtered through their own error and bias and whatever.