NOT WORKING "Duplicate to Staff below"

Hi community,
the key combination does nothing
but when i use the menu item everything works as expected…
Any ideas?

BTW: “Duplicate to staff above” works fine with its key command.
I also tried reassigning it to M in the key commands, but the letter M shows no reaction, if i use B instead no problem…
I have a german keyboard, but english program language.

See here for how to change the Dorico keyboard lanaguage, or to double-check that the Dorico keyboard language matches your keyboard:

Your keyboard language must match your keyboard or the shortcuts won’t reliably work.