The Unbreakable JG passive skill is not working

I'm playing RF build and just completed the last trial and unlocked this skill but the armor value was not doubled as the skill says, what should I do? Or maybe it has to be triggered somehow? is it a bug?

You won't see the difference by looking at body armour.

This mod contributes to your total armour which you can check in the character panel (C- Defence). Since you already got the notable, PoB can help you to calculate your armour before you took it.