Server Script
local remote = game.ReplicatedStorage:WaitForChild('RemoteEvent') remote:FireAllClients('Part')
Local Script
local remote = game.ReplicatedStorage:WaitForChild('RemoteEvent') remote.OnClientEvent:Connect(function(player,Part) print(Part,player) end)
There is no player argument. you are firing from the server to the players.
the parameter for the localscript is only "Part", no 'player'.