Tekahn,Plague Lord Of Flame

Hi when I complete the fight against Tekahn The Plague Lord Of Flame. It doesn’t give me the reward and makes me do the fight again. It takes a lot of attempts to beat this fight and I have just managed to record the final blow once more and the fact that the mission loops for me. Please help. I am trying to complete all of the Solo Quests and this one is really frustrating me. Please help. Thank you.