Fomorian King mission bug lvl.26 (King Arthur: Knight's Tale)

I pass the quest Fomorian king lvl.26 and after that there is no "complete" mission.
Replayed 2 times, killed the boss. There is only one result - I just stay at the location without the opportunity to leave the quest. I looked on YouTube - there, after killing the boss, the "complete" button immediately appears.
Actually, ideas? Offers? Wishes?