In order to enchant a skill, you may have to find a specific NPC. There are currently 22 NPCs in the game that allow Skill Enchantment; among these, you must find the one who fits both your race and your occupation or the enchantment cannot progress. Listed below are the NPCs you should seek:
Sedrick's Training Hall in the Town of Aden: Master Aiken, Master Sinden
Einhasad Temple in the Town of Oren: Priest Vadin, Priest Egnos
Oren's Ivory Tower: Magister Marina, Magister Joan, Magister Ladd
Hardin's Academy: Master Galadrid, Magister Anastia, Dark Knight Mordred, Lich King Icarus
Fighters Guild in Hunters Village: Master Aren Athebalt, Master Stedmiel
Rune Township Fighters Guild: Prefect Tazki
Rune Township Sage's Library: Seer Mekara
Rune Township Blacksmith: Blacksmith Vincenz
Rune Township Warehouse: Warehouse Keeper Hugin, Warehouse Keeper Durin, Warehouse Keeper Lunin, Warehouse Freightman Daisy
Kamael Village: Master Nerga, Master Xonia