Shortcut for “Show Grayscale Mask” (OPTION KEY + M) does not work when assigned to button on Loupedeck

Hi There, Im struggling to get one specific shortcut to work when assigned to a button on Loupedeck. That is the Option+ M keys for “show grayscale mask” function. It works when hitting the keys on the keyboard, but not when hitting the key on Loupedeck. I cannot find this OPTION+ M command or the “Grayscale Mask” command in the keyboard shortcuts menu as well. All other shortcuts, regardles of how complicated they are, work. But not this one. Any idea?