Can't tell if this is reddit spambot but, initial search yielded no results. So, to answer your question - void CB always placed poison debuffs.

DId your team change? It may have been you either had block debuffs up or high enough res that the poisons just never landed.

But most likely just never noticed

it was the res, i had changed my team around and it didnt even cross my mind when i did it. thanks for the information and the help.