Why does the value of the hygrometer not change and always remain at a certain value?

Why does the value of the hygrometer not change and always remain at a certain value?

1. Please turn off the power of the humidor for a while.
2. Please adjust the temperature to the lowest, lower the temperature of the humidor, and see if the humidity changes.
3. what are the ambient humidity, the desired humidity, and the humidity displayed by our hygrometer?