Discord Webhook HTTP 400 (Bad Request)?

So im trying to make it when you start a application proccess it sends me a message into a discord. But its giving me a

HTTP 400 (Bad Request) - Server - Script:15

This is the script:

local http = game:GetService("HttpService")
local event = game.ReplicatedStorage.RemoteEvent

event.OnServerEvent:Connect(function(player, squad)
    print("Fired!")
    if squad == "CIS" then
        local data = 
            {
                ["title"] = "CIS Application started!",
                ["description"] = "Player: "..player.Name,
                ["color"] = 5158332,
                ["thumbnail"] = {url = game.Players:GetUserThumbnailAsync(player.UserId, Enum.ThumbnailType.HeadShot, Enum.ThumbnailSize.Size420x420)}
            }
        local Data = http:JSONEncode(data)
        http:PostAsync("https://discord.com/api/webhooks/.../...", Data) -- Error Line
    end
end)