No notification sounds on my iPad Mini 5

Hi,

I noticed that the notification sound for my e-mail and other apps (i.e., games etc) installed in my iPad mini 5 doesn't work. I have enabled all the notification settings as well as the background apps but still can't hear the notification sound. The banner notification works properly though, but no sound.

If I selected sound from the settings, it works just fine. Please help how to fix this issues.

Thank you

AK