It seems like it at least.
I have a few set bonuses that give extra armour and/or armour toughness, but they don't seem to actually be added t o the player.

That, or the bar doesn't render them.

Kind of annoying since it defeats the purpose of the mod....

How are you declaring the attribute-based bonuses? Using the bonus from #15, here's its entry in section 3:

IceScaleArmorBonus, generic.armor = 5 @ 0, generic.maxHealth = 10 @ 0

(its entry in section 4 is this)

IceScaleArmorBonus, minecraft:resistance.1

Aye, attribute bonuses should be working fine. Here's a basic test/example config file for reference:

1.12.2.009+.zip

I used max health in this example, but armor also renders properly. Closing this one for now, but if there's still an issue, I'll see any responses here.

Hmmm...I've only noticed it apply to Armor Toughness, and sometimes armor points itself.

It could be Classic bars not picking up the changes.

Honestly I don't mind if it doesn't render on the HUD as long as it works

How are you declaring the attribute-based bonuses? Using the bonus from #15, here's its entry in section 3:

IceScaleArmorBonus, generic.armor = 5 @ 0, generic.maxHealth = 10 @ 0

(its entry in section 4 is this)

IceScaleArmorBonus, minecraft:resistance.1

Yes that's how I formatted them, the config told me so. I meant that if I change armor toughness for example, it doesn't render on the bar (could be Classic Bars not picking it up though)

Though I have mine formatted as generic.armor = 4.0 @ 1, so maybe that's why?