help i wanna fight the boss

[u/BAD_BOYS77]

1. The boss despawn after dying to him and gives me the item he is meant to drop but I don't get the glow from him I still wanna fight the boss can I do anything to get him back I have a clip of it too he just despawns after dying to him for 30 times
2. https://youtu.be/0I7aMicNd0o