As a short day plant, Kalanchoes need a little prompting in the form of temperature and light to rebloom. In fall, situate the plant a bit away from the window that gets the longest amount of light.
Ideally, the plant should get no more than 10 hours of light for 6 weeks. This must be combined with daytime temperatures of 65-70 (18-21 C), and nighttime temperatures around 60 Fahrenheit (16 C).