Dual Wield: Off hand not apply debuff

[Shion]

Hello everyone, as title says.
My rogue uses Hunter's Dagger: Main hand (ruptures if fail dc)
Sussur's dagger: Off Hand (silence on hit)

Ruptures works ok while in main hand, but silence never hit.
I set sussur in main hand and silence did not occur at all and rupture also did not while in off hand (not even rolled dc for saving).

Is it a bug or d&d rule for dual wield?
I tested sussur dagger on main hand and no off hand weapon. Silence did not apply also.

[Dr. Sinclair]

IIRC there is a hidden saving throw to apply the silence

[Shion]

Originally posted by Dr. Sinclair:

IIRC there is a hidden saving throw to apply the silence

I see. But any idea why hunter's dagger in off hand does not trigger rupture? I mean does not even trigger the test for saving. thanks