I keep getting the same error with HTTP SERVICE how would I go about fixing it?

My issue is on line 21.

02:52:11.977 - HTTP 400 (HTTP/1.1 400 BAD REQUEST)

How would I fix this?

local HTTP = game:GetService("HttpService")


local key = "" -- discord key

local HookData = {
	
	["Username"] = "";
	["Content"] = "";
	
	
	
}



game.Players.PlayerAdded:connect(function(Player)
	if Player.Name == "Fraxinus_Sanctus" then
		HookData.Content = "Fraxinus_Sanctus Has joined the game: .... Come join him!"
		HookData.Username = "Genesis Studios Admin Joined"
		HTTP:PostAsync(key,HTTP:JSONEncode(HookData))
	end
	
end)