I have a valid coupon with an expiration date that was refused at a local fast food chain. Can I now sue them?

I received a coupon from Arby’s in my email. My husband ordered food and explained the coupon. The lady at the drive through (who I now assume was the manager) refused the coupon stating that it was expired. My husband stated the expiration date was 10/4, but was met with hostility by this woman. When I called to complain about this situation and try to at least get an apology or my money back, I was met with an extremely defensive woman who told me to file a complaint with corporate & that my coupon was a forgery despite being emailed directly from Arby’s itself. We received no discount, comped food or an apology.