Hello and thank you for your comment.
You did it right, but you probably just entered the opacity value in the plugin command and left the other empty. Even if the x, y and z doesn't change, you have to give them values (same as notetag if they don't change), otherwise plugin don't know where to put the overlay and it doesn't show...
I will make an update later so you only have to enter the values you need to change.
Thanks!