The pair were photographed together at Events New Year's Eve Party on Monday night.
"They couldn't keep their eyes off one another. You could definitely sense a spark there," a source revealed.
The couple called it quits back in 2015, but Carly told New Idea that she still cares about Robert.
"We were definitely in love," Carly told the publication in October 2018, "It felt like that was it and we'd get married and end up together forever."