I killed Arbiter of ash after my death and it's bugged

As i mentioned in title, i killed arbiter of ash after my death and no item gave me(only passive book), and there is a ball named "Power Awaits You" waiting for me to touch it but i can't reach it. I had 3 more times to try to kill the boss but now there is no chance to get rewards/kill boss and click that power awaits you ball.

Same happened to me, is there anything we can do? Or i got stuck here after the first kill?
I relogged with my character and it puts me back in the same instance - i cant find an option to close & restart the instance (i rather loose a key then being stuck here)

Update - After instance closed i was able to speak with Doriani and by this way i was able to obtain the other book for the arbiter skillpoints