maybe you have a bad code, try this:
The skill itself:
<skill id="9999" levels="1" name="Block Buff">
<set name="target" val="TARGET_SELF"/>
<set name="skillType" val="CONT"/>
<set name="operateType" val="OP_TOGGLE"/>
<set name="castRange" val="-1"/>
<set name="effectRange" val="-1"/>
<for>
<effect count="0x7fffffff" name="DeflectBuff" time="3" val="0"/>
</for>
</skill>
what to fill in the base:
INSERT INTO `skill_trees` VALUES ('0', '9999', '1', 'Block Buff', '0', '1');
INSERT INTO `skill_trees` VALUES ('10', '9999', '1', 'Block Buff', '0', '1');
INSERT INTO `skill_trees` VALUES ('18', '9999', '1', 'Block Buff', '0', '1');
INSERT INTO `skill_trees` VALUES ('25', '9999', '1', 'Block Buff', '0', '1');
INSERT INTO `skill_trees` VALUES ('31', '9999', '1', 'Block Buff', '0', '1');
INSERT INTO `skill_trees` VALUES ('38', '9999', '1', 'Block Buff', '0', '1');
INSERT INTO `skill_trees` VALUES ('44', '9999', '1', 'Block Buff', '0', '1');
INSERT INTO `skill_trees` VALUES ('49', '9999', '1', 'Block Buff', '0', '1');
INSERT INTO `skill_trees` VALUES ('53', '9999', '1', 'Block Buff', '0', '1');
client:
skillgrp.dat
9999 1 3 35 -1 0 0.000000 0 icon.skill1405 0 0 0 0 -1 -1
skillname-e.dat
9999 1 Block Buff Block All Buff none none
if not working try change id skills