Scenario 1: The away mode location radius around your home may be too small, not giving the system enough time to warm up your home sufficiently. Try increasing the size of the radius boundary. [ More Menu ] > [ Away mode ] > [ Auto away mode ] > [ Away mode radius ].
Scenario 2: If you have set an adequate location radius and are within the radius boundary but your heating has not come on yet, it may be because heating is not scheduled to turn on.
If your house is above the frost protect temperature, your heating will not turn on until the next scheduled heating event. If this happens regularly, you should consider adjusting your heating schedule to start earlier. Tap on the calendar icon on the top right of this screen.