Stuck in the Niko Mining Encampment questline

I did part of Niko's Mining Encampment questline, but died before I could complete it. I was unable to do the final portion, as I was out of sulphite.

I had brought Niko to my hideout, and was waiting to find more sulphite.

I migrated my character from the defunct Necropolis League to Standard. Noticed Niko was no longer in my hideout. Kept playing. I got more sulphite in Act 5, and headed back to Act 3.

My quest tracker is showing the following:
Niko's Fuel (Optional)
-Visit Niko's Mine Encampment
Niko's Mine (Optional)
-Activate the Crawler

Niko's left side dialogue options:
Introduction

Niko's right side dialogue options:
Voltaxic Sulphite (See that? One moment, big blades...)
Voltaxic Sulphite (Ah, this is the stuff. Good nose, exile...)
Visit Mine Encampment

If I click on 'Visit Mine Encampment' or click on the 'click to travel to the Mine Encampment' button on the waypoint, I get a message saying "You do not have the required quest state."

Where do I go from here?