Junior status, regardless of how much longer you'll be in school, at a school with a competitive recruitment that doesn't have a separate upperclass quota does really hurt you. You didn't mention whether you had recs or if your GPA was impeccable but even if you did have great recs and a stellar GPA, when a chapter has to make cuts with little information to go on, junior class standing hurts a lot. You can't take it personally. Although sorority life is very meaningful to everyone on this board, there are MORE people who are not Greek who have a great college experience than people who are Greek.
Good luck