Dude, in each of the 3 ship plugs in custom/ships (excluding the shuttle) rename "Fed Ablative Armour" to "Ablative Armour". DJ just mistyped the name of the tech, and because of that the game can't find it.
Should look like this fixed:Foundation.ShipDef.DJEnterpriseG.dTechs = {
"Ablative Armor": {"Plates": ["Forward Ablative Armor","Aft Ablative Armor","Dorsal Ablative Armor","Ventral Ablative Armor"]}
}