POE2 - First boss of the act 2 is glitched, I can't progress. HELP

This evening, I suddenly encountered a strange phenomenon. I wanted to start progressing through the second act. I met the boss, had a brief fight, and then, just a few moments later, the following happened: I ran out of his area, that elevated platform, to restore my resources, and then returned. Here's what I saw—the boss was standing there, not moving. I thought, "Let me approach and try to fight him." Turns out, he regenerates so much health per second that I can’t outdamage it.

At this point, I don’t know how to progress in the game. I’m not sure if this boss is mandatory or optional. Still, I don’t want to skip part of the content, and I’m interested in defeating him. I think he might be part of the story quests, but I’m not certain.

I hope the developer or support team will respond to my message soon. I’d be glad to know how to restart this cycle, as it might help. Thanks in advance!

https://imgur.com/a/RWXzcnc