After you have set the Customized Scene settings, you must apply them for use in Day /Night Switch.
You can then use Time Plan Settings to set a time based schedule, if you choose
edit: When you click on Day/Night Switch, double check that your Day/Night settings that you set under Customized Scene are the same, then click Apply.
Have been using a LUX sensor to trigger a Dahua API to change day/night modes on a BI system for all cams. While time around sunrise/sunset works, LUX takes into account cloudy vs sunny conditions and switches modes based on light levels vs a preset time.
The mode change is only active during a window based on calculated local sunrise/sunset. The mode changes when a preset LUX value is reached. Works on both Web 4 and Web 5 Dahua cams.