FireClient doesn`t work when firing it from a OnServerEvent. Can it be done or i need to change it?

Hi! Can someone explain to me why when im trying to FireClient it says attempt to index nil with 'FireClient'(the player name prints in print(player.Name)). Any answer is appreciated.

This is the code

  local replicatedStorage = game:GetService("ReplicatedStorage")
  local ClaimClientMD = replicatedStorage:FindFirstChild("ClaimClientMD")
  
  local function MoveDown(player, claimPart)
  	print(player.Name)
 	local claimPart1 = claimPart
 	local X,Y,Z 
  	X = claimPart.Position.X 
 	Y = claimPart.Position.Y 
  	Z = claimPart.Position.Z
  	claimPart.Position = Vector3.new(X,Y-15,Z)
 	ClaimClientMD:FireClient(player, claimPart)
  end
  
  
  replicatedStorage.Remotes.ClaimMoveDown.OnServerEvent:Connect(MoveDown)