Shortcut for screen brightness stopped working

The screen brightness adjustment stopped working. if i hit fn and the arrow keys the brightness popup on the upper right pops up but with the keys i cannot adjust screen brightness. With the mouse it is adjustable.

The audio volume is adjustable via keyboard, panel brightness is not.

Can someone help me out, it suddenly stopped working.
Also i was able to turn the panel completely off via shortcut, via mouse this isnt possible anymore.