High Priest Prana:
You need the appropriate level and token to become an Elven Wizard. To change profession, your level must be at least 20, and to become an Elven Wizard, you must have the token that proves that you passed the Test of the Elven Wizard.
It seems you have passed the Test of the Elven Wizard, but you cannot change profession because your level is lower than 20. If your level is lower than 20, you cannot change profession, even if you have a token. Please come back when you are ready.