Thats maybee a stupid question, are you pressing shift only ? If so -this wont work. It´s the macro key (where you placed the macro symbol) + shift. If the Spell is on Cooldown and you press shift the whole macro stuck.
Also it maybee depends how fast you push the macro key (30-60ms is good for a melee in my experience)
It also don’t fire the “shift” spell immediately, it can take a short moment.
If you are a long time user than forget my answers..hopfully someone else will help you than 🙂
Code + Macro + Code = Blackbox