If you're using L2J latest branch, they change XML format file.
Check how is build the others XML in datapack and fix the tags. Is easy to understand the new format.
Also if you have old custom_npc, custom_spawnlist, custom_drop, and so, you need to create XML instead of put it into the database as well.
Everything can be found under:
1- game/data/stats for NPC, skills, droplist, and so
2- game/data/spawnlist for spawnlist
Let us know your results.