Sense is currently only supported on SuperPods, so if the room only has PowerPods, you will not necessarily get Sense coverage in there.
Since each SuperPod will only use 3 WiFi devices at a time, it is also possible that there are no devices near or in that room being used to detect motion, which is why there is no coverage. You can choose which devices are used for Sense by following the instructions here.
We recommend assigning devices to a room through the HomePass app to improve the personalisation and accuracy of motion alerts.