The Trials of Chaos - “The Operation could not be completed.” (Problem resolved)

Keep receiving the captioned error message. Tried relog, close game, switch to other character, none of the above works.
This is the green “Chimeral Inscribed Ultimatum” (Lv38) - (2nd Ascension is stuck!) Tried switching to other inscribed Ultimatum (Area Lv43). Still the same error message.
Please advise if there is workaround ASAP.

(Edit:
No problem now. I reset the instance from waypoint)

Newbie question: how to remove my own message here?