Both the brennenstuhl®Connect WiFi Smoke and Heat Detector WRHM01 and the brennenstuhl®Connect WiFi Smoke Detector RM A 3020 enter a sleep mode after 7 days.
The detector is still active and will wake up again if an alarm is triggered. You can also wake the detector by pressing the test button (test alarm).
This feature is intentional to save battery. If the detector communicated continuously with the Wi-Fi, it would significantly shorten the battery life.