"Send Shortcut to Specific App" not working with Discord

I've seen a number of presets shared here that mention being able to invoke the Toggle Mute keybind for Discord. However, no matter what permissions I give BTT, I am not able to get this to work. I can send keys to Discord to make it type letters and whatnot, but I cannot get the Toggle Mute keybind to trigger.

What am I doing wrong? Any help would be much appreciated, this has been driving me nuts.