It probably isn't free wifi. Try going to a non-https website, it should hijack your page and redirect you to either a sign in page or a payment page run by the company to authenticate you on their network. Most places with public wifi have a proxy you have to go through in order to access the web. The reason tor is working is because they can't intercept it, only block it, and it's probably not configured to do so. A VPN would also probably work.