Connecting Dell laptop to Magnavox smart TV

Despite entering the SSID into my Magnavox Smart TV and using an HDMI cable I'm unable to connect my Dell to my smart TV IE use my Magnavox as a monitor. I've done it before but for some reason, it's just not working this time. I've written Magnavox customer service and spoken to ATT support. I do have a slower internet connection, down from Uverse to what they're calling high- speed 6mg. Would someone please tell me what I can do to get this TV online? Is there an upgrade or download I need?