The current civilizations.json file has 48 civilizations, while the mod data file only has 45.
If you edit the mod’s civilizations.json file and delete the last three civilizations (lines 1229 to 1308), it should work. Below is the portion to delete:
{
"internal_name": "Achaemenids",
"tech_tree_name": "ACHAEMENIDS",
"data_name": "ACHAEMENIDS-CIV",
"hud_style": "CivPersian",
"tech_tree_image_path": "/resources/civ_techtree/menu_techtree_achaemenids.png",
"emblem_image_path": "/resources/civ_emblems/achaemenids.png",
"unique_unit_image_paths": [
"/resources/uniticons/621_50730.png"
],
"name_string_id": 7500,
"computer_name_string_table_offset": 106440,
"unique_tech_id_1": 499,
"unique_tech_id_2": 494,
"unique_unit_upgrade_id": 1115,
"unique_unit_id": 2101,
"elite_unique_unit_id": 2102,
"unique_unit_string_ids": [
{
"name": 414001,
"description": 426001
}
],
"era" : "antiquity"
},
{
"internal_name": "Athenians",
"tech_tree_name": "ATHENIANS",
"data_name": "ATHENIANS-CIV",
"hud_style": "CivGreek",
"tech_tree_image_path": "/resources/civ_techtree/menu_techtree_athenians.png",
"emblem_image_path": "/resources/civ_emblems/athenians.png",
"unique_unit_image_paths": [
"/resources/uniticons/624_50730.png"
],
"name_string_id": 7501,
"computer_name_string_table_offset": 106460,
"unique_tech_id_1": 499,
"unique_tech_id_2": 494,
"unique_unit_upgrade_id": 1125,
"unique_unit_id": 2104,
"elite_unique_unit_id": 2105,
"unique_unit_string_ids": [
{
"name": 405003,
"description": 426003
}
],
"era" : "antiquity"
},
{
"internal_name": "Spartans",
"tech_tree_name": "SPARTANS",
"data_name": "SPARTANS-CIV",
"hud_style": "CivGreek",
"tech_tree_image_path": "/resources/civ_techtree/menu_techtree_spartans.png",
"emblem_image_path": "/resources/civ_emblems/spartans.png",
"unique_unit_image_paths": [
"/resources/uniticons/622_50730.png",
"/resources/uniticons/623_50730.png"
],
"name_string_id": 7502,
"computer_name_string_table_offset": 106480,
"unique_tech_id_1": 499,
"unique_tech_id_2": 494,
"unique_unit_upgrade_id": 1135,
"unique_unit_id": 2107,
"elite_unique_unit_id": 2108,
"unique_unit_string_ids": [
{
"name": 405031,
"description": 426031
},
{
"name": 405005,
"description": 426005
}
],
"era" : "antiquity"
}