En effet, et c'est tout à fait normal !
Tu as fait un PlayerScript, donc si tu veux qu'il se passe quelquechose en jeu, tu dois implémenter une ou plusieurs méthodes du PlayerScript, que voici ci-dessous.
void OnPVPKill(Player* killer, Player* killed);
void OnCreatureKill(Player* killer, Creature* killed);
void OnPlayerKilledByCreature(Creature* killer, Player* killed);
void OnPlayerLevelChanged(Player* player, uint8 oldLevel);
void OnPlayerFreeTalentPointsChanged(Player* player, uint32 newPoints);
void OnPlayerTalentsReset(Player* player, bool noCost);
void OnPlayerMoneyChanged(Player* player, int32& amount);
void OnGivePlayerXP(Player* player, uint32& amount, Unit* victim);
void OnPlayerReputationChange(Player* player, uint32 factionID, int32& standing, bool incremental);
void OnPlayerDuelRequest(Player* target, Player* challenger);
void OnPlayerDuelStart(Player* player1, Player* player2);
void OnPlayerDuelEnd(Player* winner, Player* loser, DuelCompleteType type);
void OnPlayerChat(Player* player, uint32 type, uint32 lang, std::string& msg);
void OnPlayerChat(Player* player, uint32 type, uint32 lang, std::string& msg, Player* receiver);
void OnPlayerChat(Player* player, uint32 type, uint32 lang, std::string& msg, Group* group);
void OnPlayerChat(Player* player, uint32 type, uint32 lang, std::string& msg, Guild* guild);
void OnPlayerChat(Player* player, uint32 type, uint32 lang, std::string& msg, Channel* channel);
void OnPlayerEmote(Player* player, uint32 emote);
void OnPlayerTextEmote(Player* player, uint32 textEmote, uint32 emoteNum, uint64 guid);
void OnPlayerSpellCast(Player* player, Spell* spell, bool skipCheck);
void OnPlayerLogin(Player* player);
void OnPlayerLogout(Player* player);
void OnPlayerCreate(Player* player);
void OnPlayerDelete(uint64 guid);
void OnPlayerSave(Player* player);
void OnPlayerBindToInstance(Player* player, Difficulty difficulty, uint32 mapid, bool permanent);
void OnPlayerUpdateZone(Player* player, uint32 newZone, uint32 newArea);
Comme tu peux le constater, ta méthode System_SpellCFix(Player *caster) n'est pas dans la liste, donc celle-ci ne sert à rien car elle ne sera pas utilisée.
Il faut donc renommer ton System_SpellCFix(Player *caster) par
void OnPlayerSpellCast(Player* player, Spell* spell, bool skipCheck);