Star beast staff bug no damage proc

[Popcute0]

So i try every boss and mob in the game the staff work proc everything but except one place that is ENKENTA'S LAIR
I try to proc with mine star beast staff ofc 6/6 star but the BOSS dont lose 1hp and the proc of weapon count down every time i try. I dont know this was a feature of the game or not . Please light me up Supporter.

[Futumsh]

Ekenta is immune to dots.