Character: Iyr, level 110 warlock, Legion x4

Argus quest [The Prophet's Gambit] to unlock Krokuun is bugged

https://www.wowhead.com/quest=46732/...ambit#comments

Everyone disappears when prophet Velen and Turalyon finish talking and can't complete this quest.

I have tried relog, going to Vindicaar and back, abandon and re-take quest. Nothing works. Need help to complete this quest which is part of quest series to unlock all flight points and world quests in Argus. Help please, thanks.