Huawei P8 MAX with smart cover have problem notification

Hello,

I just got p8 max today. everything is good, high quality built , huge battery.

but I have problem with my smart cover, when I use this cover , Application Line is no longer have a sound notification at all , it just lid up to show date and time in dot view case .when I open cover it's show line preview message as normal.

if I detach smart cover , line notification is act normally have sound with preview message.

I wonder how to solve this problem.

I already turn LINE notification center to ON .

and already turn LINE in Protect Mode.

but the dropzone management has not LINE app to turn on.

Sorry for my grammar
Thank you

ps. facebook messenger has no problem , work like a charm