failed to connect to instance for only ONE of my characters

Hi i have several characters in my account but since an hour ago, i cannot log in to my mercenary which is in cruel act 3. It keeps saying failed to connect to instance.

Please advise on what to do. All my main items, astramantis, and ingenuity belt are in the character.

i have restarted, verified integrity of files. all other characters seems to work fine.