Duplicate Sniper's Blizzard does not work sometimes

I have a Sniper and the level of Blizzard is 21 now, however I have noticed that the blizzard does not work sometimes.

For example: there were 4 monsters(of course they can be frozen), but sometimes maybe 2 of them cannot be frozen regardless of ho

Wish it could be fixed as soon as possible.

thank you.

 

Change your compatibility to windows xp service pack 3.