PostAsync not working?

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

local webhook = "https://webhook.lewisakura.moe/api/webhooks/1225225070939475968/kkixc5_QIYybIdQ    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
	})
	print("a")
   
	HTTP:PostAsync(webhook, payload)
	
	print("b")
	
    return "Received"
end

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