[DubaiSis]

Unfortunately no, nobody can tell you why. But based on what you posted above,

there were no one on one talks. just ice breakers. so there really was not a chance for me to talk. and i was really nervous

this is probably why. You probably needed to be more aggressive and jump into the fray more than you did. It's unfortunate when chapters don't follow a system to ensure they meet every girl who has gone out of their way to meet the sisters, but when they haven't, you have to make up the difference.

You didn't give us much information so I'm going to make a few guesses and maybe it will help.
1-you are a freshman. You can try again next year (depending on your school, you can try again as a sophomore as well, or even a junior but then your chances start decreasing rapidly)
2-not every chapter is at total and will be doing some informal rushing. You can talk to the Greek life office about that.
3-you didn't go in prepared with conversation skills, appropriate wardrobe, appropriate attitude. Spend some time thinking about what you did versus what other girls did and why their outcome may have been better.
4-were your grades good enough?

You shouldn't beat yourself up about this but do spend some time thinking about what you could have done differently/better, and then move on with your life. Making friends. Being active on campus, doing things that make you happy, around other people, these are all things that will make you a better candidate next time. And if it was or might have been your grades, get yourself in some study groups. It will help your grades and help you get to know some people in your classes.