Solution:
The working principle of this function is to rely on the acceleration sensor inside the watch. You can wake up the screen by tilting your wrist, such as turning your wrist or raising your wrist. However, if the wrist turning angle is too small, the speed may be too slow, which may cause the problem that the screen cannot be turned on. If you need to recognize the wrist lift more sensitively, you can select the response speed as sensitive in Mi Fitness APP->Profile->Wrist-lifting to brighten the screen->Response speed.
Note: Turning on responsive speed will reduce the battery life of the watch.
Does it help?