Grand Master Pabris:
To become an Elven Scout, you need the appropriate level and token. Your level must be at least 20 to qualify to change profession. You need a token to prove you have passed the Test of the Elven Scout, as well.
I am satisfied with your level, but it seems that you have not passed the Test of the Elven Scout. You can become an Elven Scout only if you pass the Test of the Elven Scout. Ask Master Reisa at the town of Gludio about the test. To become an Elven Scout, you must pass her test and bring back her letter of Recommendation.