I am trying to use windows new Dictation feature, holding down CTRL and H keys, but no listening toolbar shows as it is supposed to.
Você está usando o atalho de teclado incorreto. Você deveria usar o Windows + H
Windows 10’s Fall Creators Update makes voice dictation much easier to use. Now, you can immediately begin dictation by pressing a key Windows+H on your keyboard. You don’t have to dig through the Control Panel and set anything up first.