‘Hardware Keyboard’ menu missing even after attaching ipad pro to the magic keyboard

I snap my ipad pro to the magic keyboard and the Hardware Keyboard menu flashing but then dissapeared (Setting>General>Keyboard>Hardware Keyboard). While the iPad is still attached/snapped to the magic keyboard, the magic keyboard behaves strangely: some buttons are not working such as Spacebar, Shift, Tab, Caps Lock, Arrows while other buttons still working.

(iPad Pro 11 2nd gen + iPadOS 15.1 + ipad pro magic keyboard)