How do I get shatter to proc? Its not showing up on my UI.
You shatter if target is frozen (rooted with your frost abilities) or has a debuff from Flurry. There are no other conditions for shatter, I believe (I could be wrong).
Also debuff from Cone of Cold if talented into The Coldest Snap.
Shatter passive won’t show on your own default UI Buffs. As long as the target is frozen with Frost Nova, Icy Nova, or Winter’s chill, it will proc Shatter on that target on you next direct damage spell.