Huawei P40 lite 5G
It's not possible to use Wi-Fi calling
Solution 3 of 4: Your phone's software hasn't been updated to the latest version
It's recommended that you update your phone with the newest software, as the manufacturer continuously corrects errors. It's a good idea to back up the phone memory first. Before you can update the phone software, you need to set up your phone for internet.
Press Settings.
Press System & updates.
Press Software update. If a new software version is available, it's displayed. Follow the instructions on the screen to update the phone software.