Should I ask why he doesn’t like me?

A friend of mine recently told me about a colleague of his who has a huge crush on me. I was intrigued and asked him to introduce us. We met at a party and this guy was really nice, funny, and charming. I was happy to meet him and flattered because I was told he liked me. A day or two after the party though, my friend called to tell me the guy was no longer interested in me. I was surprised because he didn’t give me any inclination of not liking me when we chatted. It is upsetting me a little because I have no specific answers from him and no clue about what I may have said or done to put him off. I am wondering if I should reach out to him directly and just ask him what went wrong. My friend says this is a bad idea because I only end up sounding needy. Should I go ahead and do it anyway?
If this person doesn’t have the courage to speak with you directly, and also decides to write you off based upon one meeting, you should ask yourself if his opinion or feedback matters in any way. It’s great when someone’s honest and gives us feedback we can use to better ourselves, but all he has done here is tell your friend that he isn’t interested. Ask yourself what you hope to gain from any opinion he may have, assuming he will be honest enough to share it with you. Sometimes, it’s better to just assume some people aren’t meant to be in your life, and move on.

I want to tell my sister’s boyfriend that I don’t like him coming over to our place as often as he does, but my sister says I have no right to decide who she can bring over. My parents don’t want to get involved. What should I do?
Do what your sister and parents are doing, which is minding their own business.