Note: Do not mark your virtual keys "Persistent", if you have a save and load in the game, you're virtual keys will be gone when you load the game. You need to place them in every room. Its best to make all your buttons, then duplicate the room, so you don't have to place the buttons in the room again.
Events: Be sure to use "Room Start" on all your virtual keys, if not, the virtual keys will disappear once you resume game again, and the buttons will not work on device.
Be sure "Room" under views tab, view in room and port on screen is set W: 3300 and H: 1991 if that is the size of you're room.
Be sure display set gui has the same wview size and hview size as what is stated above 3300, 1991 so that the virtual keys remain locked in there locations on the buttons, even if you press pause and then resume game. If you don't have the same Weight and Height for you're GUI as you're room size, then the virtual keys will not be on the buttons, and the buttons will not work.