It plugs into the electrical ports on the wand right? Only lighting up when the triggers pulled. 

Alright! Two scenarios in my view. One. it isn’t compatible with your stick vac. It will only light up if there enough power from the motor. The purchase page should cover this. if not, this post can explain it better than I can. Dyson Cordless vacuums: Understanding the tools and accessories | Dyson Community. 

Two. It arrived faulty. In this case, the seller should replace it free of charge !