The mod is missing the forge tags for the Neptunian tools and armor. So tags like forge:armors/helmet or forge:tools/pickaxe
That also affects the Neptunian pickaxe's inability to break amethyst crystals.

As you can see, the pickaxe lacks the minecraft:cluster_max_harvestable. Meaning that if I use that pick to break amethyst crystals, I just get 2 shards instead of the usual 4.