Advancements Help

ok so i have an issue with a datapack i am working on. basically i have an advancement that is not loading. the file path is: \data\dragonsummoning\advancements\kill_strato_dragon.json and the file itself is: { "display": { "icon": { "item": "minecraft:dragon_head" }, "title": { "text": "Stratospherical End", "color": "gold" }, "description": { "text": "Kill the Stratospherical Shard of the Dragon", "color": "yellow" }, "frame": "challenge", "show_toast": true, "announce_to_chat": true, "hidden": false }, "criteria": { "requirement": { "trigger": "minecraft:player_killed_entity", "conditions": { "entity": [ { "condition": "minecraft:entity_properties", "entity": "this", "predicate": { "type": "minecraft:ender_dragon", "nbt": "CustomName:'{\"text\":\"Stratospherical Shard of the Dragon\"}'" } } ] } } }, "rewards": { "function": "dragonsummoning:leavestrato", "loot": [ "dragonsummoning:strato_dragon_death" ] } } can anyone see any glaring errors that i have made, and that would cause the advancement to not work?