High Prefect Castor:
Basically, to be qualified for a Monk, your level must be at least 20 and you must pass the Test of the Monk.
It seems that you have passed the Test of the Monk, but your level is not high enough. 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. Come back when you have increased your level.