Why isn't this web-hook ban log not working?

Here's the script:

local webhookURL = "" --There is a webhook, I'm just not showing it.
local HttpService = game:GetService("HttpService")
local Players = game:GetService("Players")

game.ReplicatedStorage.ModEvents.BanPlayerLogs.OnServerEvent:Connect(function(player, Evidence, Username, Reason)
	local thumbnail = Players:GetUserThumbnailAsync(player.UserId, Enum.ThumbnailType.AvatarBust, Enum.ThumbnailSize.Size420x420)
	
	if game.JobId == "" then
		serverId = "N/A"
	else
		serverId = tostring(game.JobId)
	end
	
	local data = 
	{
		["content"] = "",
		["embeds"] = {{
			["title"] = "",
			["type"] = "rich",
			["color"] = tonumber(0xFF0000),
			["thumbnail"] =  {
			    ["url"] =  tostring(thumbnail)
			},
			["fields"] = {
				{
					["name"] = "**Player**",
					["value"] = string.format("%s | %s", player.Name, player.UserId),
				},
				{
					["name"] = "**Action**",
					["value"] = "Banned Player.",
				},
					
				{
					["name"] = "**Info**",
					["value"] = "Player banned: "..Username.."\n \nBanned by admin: "..player.Name.."\n \nReason: "..Reason,
				},
					
					{
					["name"] = "**Evidence**",
					["value"] = Evidence,
					},
					
				{
					["name"] = "**Server ID**",
					["value"] = serverId,
				},
			}
		
		}}
	}
	
	local jsonData = HttpService:JSONEncode(data)
	
	HttpService:PostAsync(webhookURL, jsonData)
end)

In the output, it says: "HTTP 400 (Bad Request)"