Basic Ai on Tower

Trying to get this tower to cast Fireball spell when there is 1 unit in the radius

The unit script

"npc_dota_td_flamethrower" { "BaseClass" "npc_dota_creature" "Model" "models/props_structures/tower_dragon_white.vmdl" "SoundSet" "Hero_Lina" "GameSoundsFile" "soundevents/game_sounds_heroes/game_sounds_lina.vsndevts"

    "Level"                     "1"
    "ModelScale"                "1"

    "Ability1"                  "tower_flamethrower"
    "Ability2"                  "tower_splash"
    "Ability3"                  ""
    "Ability4"                  ""
    "Ability5"                  ""

    "AttackCapabilities"        "DOTA_UNIT_CAP_RANGED_ATTACK"
    "AttackDamageMin"           "25"
    "AttackDamageMax"           "30"
    "AttackDamageType"          "DAMAGE_TYPE_ArmorPhysical"
    "AttackRate"                "1.3"
    "AttackAnimationPoint"      "0.3"
    "AttackAcquisitionRange"    "900"
    "AttackRange"               "900"
    "ProjectileModel"           "particles/units/heroes/hero_dragon_knight/dragon_knight_elder_dragon_fire.vpcf"
    "ProjectileSpeed"           "1900"

    "BoundsHullName"            "DOTA_HULL_SIZE_BUILDING"

    "MovementCapabilities"      "DOTA_UNIT_CAP_MOVE_NONE"
    "MovementSpeed"             "0"
    "MovementTurnRate"          "0.5"

    "BountyXP"                  "0"
    "BountyGoldMin"             "0"
    "BountyGoldMax"             "0"

    "StatusHealth"              "150"
    "StatusHealthRegen"         "0.25"
    "StatusMana"                "0"
    "StatusManaRegen"           "0"

    "TeamName"                  "DOTA_TEAM_GOODGUYS"
    "CombatClassAttack"         "DOTA_COMBAT_CLASS_ATTACK_SIEGE"
    "CombatClassDefend"         "DOTA_COMBAT_CLASS_DEFEND_STRONG"
    "UnitRelationshipClass"     "DOTA_NPC_UNIT_RELATIONSHIP_TYPE_BUILDING"

    "VisionDaytimeRange"        "1800"
    "VisionNighttimeRange"      "1800"

    "HasInventory"              "0"

    "Creature"
    {
        "CanRespawn"                "0"
        "States"
        {
            "Invade"
            {
                "Name"              "Invade"
                "Aggression"        "100.0"
                "Avoidance"         "0.0"
                "Support"           "0.0"
            }
        }

        "DefaultState"              "Invade"

        "OffensiveAbilities"
        {
            "Ability1"              
            {
                "Name"              "tower_flamethrower"
                "AOE"               "1"
                "Radius"            "650"
                "MinimumTargets"    "1"
            }
        }
    }
}

The Spell script

"tower_flamethrower"
{
    "BaseClass"                     "ability_datadriven"
    "AbilityBehavior"               "DOTA_ABILITY_BEHAVIOR_AOE | DOTA_ABILITY_BEHAVIOR_POINT | DOTA_ABILITY_BEHAVIOR_AUTOCAST"
    "AbilityTextureName"            "ogre_magi_fireblast"
    "MaxLevel"                      "1"

    "AbilityCooldown"               "2.0"
    "AbilityChannelTime"            "2.0"

    "AbilityCastRange"              "900"
    "AbilityCastPoint"              "0"

    "AbilityManaCost"               "0"

    "AbilitySpecial"
    {
        "01"
        {
            "var_type"              "FIELD_FLOAT"
            "radius"                "900"
        }
        "02"
        {
            "var_type"              "FIELD_INTEGER"
            "speed"                 "900"
        }
        "03"
        {
            "var_type"              "FIELD_FLOAT"
            "damage"                "20"
        }
        "04"
        {
            "var_type"              "FIELD_FLOAT"
            "rotation_angle"        "90"
        }
        "05"
        {
            "var_type"              "FIELD_INTEGER"
            "projectile_count"      "12"
        }
    }

    "OnSpellStart"
    {
        "ApplyModifier"
        {
            "Target"                "CASTER"
            "ModifierName"          "modifier_channel_start"
        }

        "FireSound"
        {
            "Target"                "CASTER"
            "EffectName"            "Hero_DragonKnight.BreathFire"
        }

        "Damage"
        {
            "Type"                  "DAMAGE_TYPE_MAGICAL"
            "Damage"                "%damage"
            "Target"
            {
                "Center"            "CASTER"
                "Radius"            "%radius"
                "Teams"             "DOTA_UNIT_TARGET_TEAM_ENEMY"
                "Types"             "DOTA_UNIT_TARGET_HERO | DOTA_UNIT_TARGET_BASIC"
            }
        }
    }

    "OnChannelSucceeded"
    {
        "RemoveModifier"
        {
            "Target"                "CASTER"
            "ModifierName"          "modifier_channel_start"
        }
    }

    "OnChannelFinish"
    {
        "RemoveModifier"
        {
            "Target"                "CASTER"
            "ModifierName"          "modifier_channel_start"
        }
    }

    "OnChannelInterrupted"
    {
        "RemoveModifier"
        {
            "Target"                "CASTER"
            "ModifierName"          "modifier_channel_start"
        }
    }

    "Modifiers"
    {
        "modifier_channel_start"
        {
            "OnCreated"
            {
                "AttachEffect"
                {
                    "IsHidden" "1"
                    "EffectName"            "particles/units/heroes/hero_dragon_knight/dragon_knight_breathe_fire.vpcf"
                    "EffectAttachType"      "follow_origin"
                    "Target"                "CASTER"

                    "EffectRadius"          "%radius"
                    "EffectColorA"          "255 0 0"
                    "EffectColorB"          "255 0 0"

                    "ControlPoints"
                    {
                        "00"                "50 100 5"
                    }
                }
            }
        }
    }
}