Elegant floor length with train wedding dress or reception dress

Beautiful floor length wedding dress. I bought it thinking it would fit but it’s too small. I wear a size 10 and it doesn’t zip up. My guess is it’s close to a size 6 and I’m listing it as a small. The waist at the band is 27.5 inches. It’s at the upper ribcage. The dress has a nice weight to it but isn’t too heave. There’s a hidden zipper under the buttons. Don’t hesitate to ask for more measurements if needed.