The "Lunar Spelunker" weekly bounty in Destiny 2 requires you to loot the chests of specific Moon lost sectors: K1 Logistics (Archer's Line), K1 Communion (Anchor of Light), and K1 Crew Quarters (Hellmouth).  The lost sector in Sorrow’s Harbor (K1 Revelation) is not part of that bounty, which is why it is not counting toward your progress.  Here is why it isn't working and how to fix it: 1. You are in the Wrong Location The Problem: You are running K1 Revelation (Sorrow’s Harbor) to complete the bounty, but the bounty requires three specific other sectors. The Fix: Go to K1 Logistics (Archer's Line), K1 Communion (Anchor of Light), and K1 Crew Quarters (Hellmouth) and loot their chests.  2. The "Firewall" Misunderstanding The Problem: The K1 Revelation lost sector (Sorrow’s Harbor) is where you use the Firewall Data Fragment after you have completed the bounty, not to complete the bounty itself. The Fix: Finish the bounty, then go to K1 Revelation in Sorrow's Harbor, go to the end, look up/right for a, and use the terminal there to get the "Memory of Sai Mota" quest item.  3. Other Potential Issues Legendary Lost Sector Issue: If you are running the Legend/Master version of a lost sector, it sometimes does not count for the bounty. Ensure you are running the normal version. Did not Loot Chest: Make sure you actually opened the final chest after killing the Nightmare boss. Buggy Sector: If you are absolutely sure you are in the correct sector, exit the lost sector, go back to patrol, and re-enter, or return to orbit and try again.  Summary for Success: Complete K1 Logistics (Archer's Line). Complete K1 Communion (Anchor of Light). Complete K1 Crew Quarters (Hellmouth). Turn in the bounty. Then go to K1 Revelation (Sorrow’s Harbor) to use the key.