Guild Wars 2

I did a search and couldn’t find a thread about this. I cannot get the Sigil of superior Doom to work on my elementalist. I haven’t tested on other classes. Anyone else having this issue?

So I applied the sigil to my bow.
It says after swaping to this weapon your first atack should poison the target.
I get the buff that says my target will be poisoned,but when I atack something it doesnt poison them.Warrior/bow.