Same issue here. I have the Fig Deluxe Edition and I preloaded on Steam, and don't see the Explorer Pack. I saw some installation error though so I uninstalled PoEII and I'm redownloading it now to see if that might fix it.
I'm having the same issue, I have the premium edition through Fig and I only see the preorder bonus on Steam, not the Explorer Pack. It seems like there might be some installation issue on Steam that's preventing the Explorer Pack from showing up?