Unable to complete Main Quest - Rock-solied Protection

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Date & Time: 16/10/2017
Frequency:
World name: Louisoix
Character name: Annabel Chai
Retainer name:
NPC name: Slafborn
Monster name:
Class/Level:56
Party or solo: Solo

I had done the dungeon - The Sunken Temple Of Qarn, passed the key item - wardstone to Slafborn, the icon on his head become green color. But, he keep asking me to explore the dungeon again and pass him the wardstone.

I had tried to re-done the dungeon again via different job n level, but can't get the key item-wardstone anymore. As this is main quest, I can't abondon it. Any solution?

If not, should I buy the finished storyline $18 to settle this problem?

I don't know if this will work, but try doing an item reclaim from a calamity salvager.