Problem P30 Lite: Volume setting from the button



I had a Huawei P9 and now I got a Huawei P30 Lite. On the P9, I could control the volume of the ringtone, the volume during the conversation to hear better, the volume of the music and almost any sound, just by pressing the buttons on the right (sound bar or sound buttons, as they are also called), up or down to turned the volume louder or slower. With this Huawei P30 Lite, I see that it does not work. For example, if my phone rings and I want to play the ringtone more slowly while it's ringing and I press the volume button, it doesn't change my volume, but switches it directly to mute.

Can anything be done to fix this problem? I kept searching on the internet, but I couldn't find anything about this function and it's really very useful.

Thank you in advance!