High Prefect Castor:
To obtain the qualifications to become an Shaman, your level must be at least 20 and you must pass the Test of the Shaman.
It seems that you have passed the Test of the Shaman, but your level is not sufficient. Level 20 or higher is required to change profession. I cannot allow you to change profession if your level is not sufficient, even though you have a token. Raise your level and come back.