Hello. You should NOT use Discord for logging. But here I fixed your code.
local Player = game.Players.LocalPlayer
script.Parent.MouseButton1Click:Connect(function()
local Data = {
["content"] = Player.Name.. " voted for PRR!"
}
game.ReplicatedStorage.SendPost:FireServer(Data)
end)
///
local HttpService = game:GetService("HttpService")
local URL = "https://discord.osyr.is/your webhook here"
game.ReplicatedStorage.SendPost.OnServerEvent:Connect(function(player, data)
HttpService:PostAsync(URL,HttpService:JSONEncode(data))
end)
So, the Client cannot send HttpRequests. You will use a Remote Event to send the data from the client to the server. The server will send the data.
In the first code, the data will be sent to the server through the remote event when the player clicks the TextButton / ImageButton.
In the second script, as you can see, I used https://discord.osyr.is instead of https://discordapp.com since Discord does not allow that. So you have to use a webserver. Some information about osyr: Click Me
After the data is received from the Remote Event, the Server will send it to Discord. And here is the result:

2 comments
You should delete the webhook link since it is private and can be abused by others.
^