ACT 1 boss dont take damage and I cant teleport to town

Started a new build and got stuck on act 1 boss.
While fighting I took DC, went back and the boss dont move, take damage or anything. Just create a new character?
https://imgur.com/a/AiEPGOG

I think you've already solved it in the meantime for you.

But as a general hint:
Go to character selection screen (or logout) and wait more than 8 minutes until the map instance is closed. Then continue with a new instance (and hopefully damage taking boss).