If you have purchased a new protective sleeve for the Huawei P20 Pro that offers a window to the display, you should activate the "Smart Cover" option in the settings to have an immediate view of important notifications through the cover.
Where Smart Cover can be activated on the Huawei P20 Pro, we would like to explain this in more detail here:
1. Scroll down to "Smart Support" and select the entry from
2. Navigate to "Smart-Cover" and activate the corresponding option. You can choose from the following: Window No window Pedometer
3. Select the type of protective cover.
You should then be able to see certain information directly through the window of your new protective cover via the Smart Cover function of the Huawei P20 Pro.