Why does a black screen appear when the Always-on display is turned on?

When turning on the screen display, the screen will go black in the following situations:
1. When the watch detects that you have taken off the watch for more than 5 minutes, the screen will automatically go black to reduce the power consumption caused by the always-on screen;
2. After detecting sleep for 15 minutes, the watch will automatically turn black.
You can reset it by the following path:
On the watch, open [Settings] APP >> [Display] >> [Always-on display] >> [Scheduled] >> turn on the option and set the time as your preference. This operation will affect the battery life.