Corrupted nexus boss did not spawn no quest credit

I completed the step to Complete a Tier 12+ Corrupted nexus.
I did it with a Tier 15 stone with 4 modifiers. Died on the boss but killed her on next try. The corrupted boss did not spawn. Cleared the nexus and corrupted zone but got no credit for the quest.

map's content gets wiped if you die at the boss. not a bug.