13:16:00.005 Player is not a valid member of DataModel

error is:

  13:16:00.005  Player is not a valid member of DataModel 

script is:

game.ReplicatedStorage.Ban.OnServerEvent:Connect(function(plr,Player,Error)
	if game.Player:FindFirstChild(Player) == nil then
		Error.Visible = true
		wait(3)
		Error.Visible = false
	else
		local PlayerToBeBanned = game.Players:FindFirstChild(Player)
		PlayerToBeBanned.BanItems.Player.Value = plr.Name
		PlayerToBeBanned.BanItems.IsBanned.Value = true
	end
end)

(not full script, but this is the area where the error was.)

error on:

if game.Player:FindFirstChild(Player) == nil then

I think you meant game.Players instead of game.Player. You probably want to replace :FindFirstChild(Player) with :FindFirstChild(Player.Name) as well.

Do

game.ReplicatedStorage.Ban.OnServerEvent:Connect(function(plr,Player,Error)
        local Fakeplr = game.Players:GetPlayerFromCharacter(Player.Character)
	if not Fakeplr then
       
		Error.Visible = true
		wait(3)
		Error.Visible = false
	else
		local PlayerToBeBanned = game.Players:FindFirstChild(Player)
		PlayerToBeBanned.BanItems.Player.Value = plr.Name
		PlayerToBeBanned.BanItems.IsBanned.Value = true
	end
end)

this will most likely work!

That didn’t work. but I fixed it now!