Currently in the chaos sanctuary hell difficulty where u have to activate 5 seals for Diablo to spawn in. After I activate 2 of the seals Diablo will appear but he can’t be damaged at all. Have tried attacking him for 20 minutes and nothing. I have tried resetting the game but every time after two seals are activated he will spawn and can’t be damaged. I have tried activating all 5 seals but that doesn’t seem to do anything. Any thoughts on what I should do ?
Are you playing on ladder?
What do you mean by " resetting the game"?
I have a strong feeling you encounter Uber Diablo.
Did Diablo spawn in the center of the area?