Despite a multimillion investment and a new partnership with the National Football League, Pizza Hut still hasn't been able to spark a successful turnaround.

Pizza Hut remains a dark spot for Yum Brands, which also owns KFC and Taco Bell, as it has struggled to differentiate itself from competitors and attract new customers.

The pizza chain has been trying to boost sales and increase the number of people coming to its restaurants. Its parent company even committed to a $130 million investment in 2017 to upgrade equipment, improve its technology and boost its advertising.

In the last year, Pizza Hut has ramped up its value offerings, offering items such as large two-topping pizzas for $7.99 and $5 menu deals. It has also begun marketing more heavily, especially during football games, as it became the official pizza sponsor of the NFL earlier this year. It's also working on improving its digital platforms to make it easier to order food online or with mobile devices.

However, this strategy hasn't exactly panned out the way executives had hoped. In the third quarter, same-store sales fell 1 percent at the brand, continuing a trend of lackluster growth.

Despite Pizza Hut's weak growth, Yum Brands expects same-store sales across all three of its brands to be up between 2 percent and 3 percent in 2019, due to the strength of KFC and Taco Bell.