It is not about the app or web browser. It is about the PI agent 2.0 in which scheduling feature is not currently available Raspberry Pi Agent 2.0.
there is a workaround to this, you have to add a new device using cayenne MQTT python library and add a custom button widget to turn ON/OFF relay. then you add a schedule to this button widget.GitHub - myDevicesIoT/Cayenne-MQTT-Python: Python Library for Cayenne MQTT API