custom advancement trigger not working

{
  "display": {
    "icon": {
      "item": "minecraft:stone"
    },
    "title": {
      "text": "CheyTac M200 Black Gold Camouflage"
    },
    "description": {
      "text": "Progress +1"
    },
    "frame": "task",
    "show_toast": true,
    "announce_to_chat": true,
    "hidden": false
  },
  "criteria": {
    "camo_m200_killcount": {
      "trigger": "minecraft:player_killed_entity",
      "conditions": {
        "entity": {
          "type": "minecraft:player"
        },
        "killing_blow": {
          "type": "minecraft:damage_source",
          "direct_entity": {
            "equipment": {
              "mainhand": {
                "item": "tacz:modern_kinetic_gun",
                "nbt": "{GunId:\"suffuse_m200\"}"
              }
            }
          }
        }
      }
    }
  },
  "rewards": {
    "function": "codmc:camo_m200_scorecount"
  }
}