Until the most recent patch, my two Sorcs (level 87 and 69) were able to use Frost Nova 100% reliably. It would guaranteed freeze anything that was not a boss. This is now no longer the case. Many Elites are now completely freeze-proof, despite having no affixes that suggest they might be.
Is this a bug or a nerf? It is killing me basically.
In season or on eternal too?
Which elites? So I can go check if it is happening to my character also. My Sorc is on Eternal.
Seems to be working just picked some random elites.
Eternal. Most recent NM dungeon I ran was full of Spider elites. A few did not freeze (it’s not all, it’s just occasionally but I’ve found an Elite which did not freeze on first attempt will never freeze no matter how many times I try. I’ve left such Elites as last creature standing and experimented. They will NOT freeze if it fails first attempt.
Ok let me find some spider elites…
Everything else runs fine right just this ability? I mean we can rule out lag on the server?
Not lag. Everything else around me froze just fine.
So just did Sarat’s Lair NM46. All spiders. Only one elite did not freeze on Nova, one of the named ones, and I suspect it was because he jumped back a bit when I did it, so more likely I missed 
The rest all froze to Nova. I did get disconnected before the boss fight though. So maybe servers?
Do you remember your Dungeon Affixes? Maybe one was “Monsters take XX% less Cold damage.” or “Monsters become Unstoppable when life drops below XX%”.
Those two could make it seem like it was not working 
Well I’ve played 100s of hours using Nova and this is only since patch.
If this is happening in a NM dungeon, check affixes. Unstoppable Monsters might be the cause.
Just had a Skeleton Elite I could not freeze. Was in a NM dungeon (Betrayer’s Row) with no affixes related to freezing. The only affix close to that was 40% reduced CC duration. The only affix the Elite had was Vampiric. No other enemies around. Tried Novaing him a half dozen times with no effect, except slight stagger animation (and took vulnerable state)
Doesn’t happen very often. Maybe 1 Elite in every 20 or 30?
Mine works just fine 99.9% of the time. I know what you’re talking about though. I just chalked it up to that they have some kind of immunity mechanic I’m not aware of. Either got CC’d too much or have some form of unstoppable from somewhere. This has been the case all season - not related to any recent patch.
I have noticed it as well on some elites. I might hit them 3-4 times with nova and still not frozen them and then when they are near dead, it might freeze them. But, i noticed this only in the last week or so.
unstoppable NM affix?
It it’s not the unstoppable dungeon affix, the next question is whether you have multiple forms of cc in your build? The other possibility is a minor cc is being applied and the monster is enjoying its period of immunity when that expires. I know this happens to me, and I see monsters that have immunity shrug off Frost Nova. You see it on elites because they have enough HP to last long enough for it happen - minor mobs just die too fast to see the effect.
This thread seems to discuss the same mechanic.
Either you missed, had poor latency, there is a bug, or they are unstoppable and you don’t realize it. You’ll see a horeshoe like thing over their head if they are unstoppable.