PostAsync not working?

I’m trying to get feedback from players in a message box. Here’s the server side:

local webhook = "    etc..."
local filteringFunction = game.ReplicatedStorage.FilteringFunction 
local HTTP = game:GetService("HttpService")
function filteringFunction.OnServerInvoke(player, msg)
    local payload = HTTP:JSONEncode({
        content = msg,
        username = "Feedback Bot - New Feedback by "..player.Name
	HTTP:PostAsync(webhook, payload)
    return "Received"

I know PostAsync is the one not working because it prints a but not b. I’m using a proxy, so that may be the problem