When you poke your IWT button, if your characters don't run to the target it can be a combination of a couple things.

1) Your followers have to assist your leader (This way they know what to interact with)
2) IWT button has to be bound and activated across all characters (This way they know they're supposed to interact) [Under keybindings in WoW]
3) Click to move has to be activated. (This way they run to the thing they're supposed to interact with) [Under mouse options in WoW]