Mowzie's Mobs Question - Can't Activate Supernova Ability with Sun's Blessing

Trying to get some help for my son who is very determined to use this Supernova ability using the Sun's Blessing from Mowzie's Mobs. I've tried this on Bedrock edition through PC and our Switch but cannot seem to activate the Supernova. I crouch and get a message that Supernova is being prepared but I cannot activate the actual move. The add-on's wiki says "Pressing shift, left mouse, and right mouse simultaneously pulls in nearby entities and creates a fiery explosion" but it's not working.

Anyone know what I'm doing wrong?