Dish Restaurant refusing to honor legally-purchased gift certificates La Canada California

About 6 or 7 months ago, my fiance and I went to Dish to use a $50 gift certificate she had received for Christmas 2014. We enjoyed our meal, then presented the gift certificate. Shockingly, Dish refused to honor it, claiming that they changed hands in February or so of 2015, and that they only honored previous certificates for the first 5 months after they changed hands. I saw on Yelp that I am not the only person having this problem. If it was a different business in the same location, I could understand, but this was the same business before as after -- only the owner chaned. The thing is, it wasn't the *owner* who sold the certificate, it was the *business*. Since the business was the same, there is no reason for them not to honor the certificates, particularly since the business stayed the same.