It should activate every time, unless you get a weak hit against a red affinity

It's not, its been around 5 days just trying to see if maybe i was not sure how it works but still the same, it won't critical all the time

I can assure you critical hits are fine, not a bug. 

There are reasons you won't crit, affinity related issues and certain Hydra situations come to mind. But, crit in general is fine.