If you asked me out, and we chatted? I'd say yes or no depending on what I'm looking for at the time and if I'm even available for dating. It is not that you lack anything. Maybe her poly plate is just full right now.
It doesn't make you HORRIBLE or anything. Or her. Just... time management.
We didn't even discuss that I am interested in poly. (When we first met, I'd apparently given her the impression that I was mono and vanilla). Having been exposed to her poly world (for the last year), I feel like exploring both worlds.
If you think that wasn't put out there clearly, put it out once more but if there's no spark for her there's just no spark for her. Be friends and let it go.