On ios device shortcut seems to be ignored. it comes in play only when screen is tapped. 

Attached example can be used to reproduce this.

Steps to reproduce:
– Run the attached project on an iPad or iPhone with an external keyboard connected (or iPad keyboard cover)
– Press the space key
– Expected: Color should change.
– Result: Nothing, Shortcut is ignored.
– Workaround: Tap the screen once. Then the Shortcut works.