ACT 4 Boss Bug

im having a problem in progressing the game, in ACT 4 "The Search: Confront Kanu and the First Herald" i already defeat the Herald but i died during that time when i resurrected at the checkpoint then this happen that i cannot proceed anymore from the game because i cannot fight again the first herald to proceed with the story and the gate still close to proceed with supposed to the next story, please see photo for your reference. Quest is still available but no First Herald and the Gate still close.