Change "<Row" to "<Replace"
Used in a XML file placed in the <UpdateDatabase> section, <Replace> will tell the game "Replace existing entries or add new ones", while <Row> says "Add new entries" and that will fail (meaning the whole file is not loaded) if there is already an entry of that type in the game's database
for example the couple Era="ERA_ANCIENT" Unit="UNIT_SETTLER" must be unique in the table MajorStartingUnits, you can't add a new one with <Row> but <Replace> will update the existing entry with the new values.
Used in a XML file placed in the <UpdateDatabase> section, <Replace> will tell the game "Replace existing entries or add new ones", while <Row> says "Add new entries" and that will fail (meaning the whole file is not loaded) if there is already an entry of that type in the game's database
for example the couple Era="ERA_ANCIENT" Unit="UNIT_SETTLER" must be unique in the table MajorStartingUnits, you can't add a new one with <Row> but <Replace> will update the existing entry with the new values.