Bugged Challenge

After killing the Act 7 boss twice for the Act Adversaries II challenge, it still tells me that the Act 7 encounter is incomplete. I've killed the other bosses and completed the campaign, it's just this one that's giving me issues so far.

I'm having the same issue, just beated it twice and didn't count for me as well. It's the same boss Arakaali

I have the same issue

I am having same issue as well.