I made a script so that when the player clicks the player will place a block?

So Try This For The Local Script:

-- Get Player
local Player = game.Players.LocalPlayer

-- MainThings
local TileGrid = workspace.Build1.Tiles
local Mouse = Player:GetMouse()
local TargetedBlock

-- Border
local Border = Instance.new("SelectionBox")
Border.Parent = workspace
Border.LineThickness = .01
Border.Color3 = Color3.new(255,255,255)

-- Services
local RunService = game:GetService("RunService")

-- Block Data Handler
local BlockSize = Vector3.new(3,3,3)
local BlockMaterial = Enum.Material.Wood
local BlockColor = BrickColor.White()



-- Events
local PlaceBlock = game.ReplicatedStorage.PlaceBlock
local RemoveBlock = game.ReplicatedStorage.RemoveBlock

-- Make Border on Targeted Block
RunService.Heartbeat:Connect(function()
    local Target = Mouse.Target
    if Target then
        if Target.Parent == TileGrid then
            Border.Adornee = Target
            TargetedBlock = Target
        else
            Border.Adornee = nil
            TargetedBlock = nil
        end
    end
end)

-- Create Block on Click
Mouse.Button1Down:Connect(function()
    if TargetedBlock then
        if Mouse.TargetSurface == Enum.NormalId.Top then
            print("Attempt to place block")
            PlaceBlock:InvokeServer(BlockMaterial, BlockColor, (TargetedBlock.Position + Vector3.new(0,3,0)))
        end
    end
end)

You Do Not Have To Send The Player Value As It Automatically Sent With The Extra Data.

If That Doesn't Work Then Instead Of Using A Remote Function Use A Remote Event And Then All You Have To Do Is Use The Scripts Below:

Local Script:

-- Get Player
local Player = game.Players.LocalPlayer

-- MainThings
local TileGrid = workspace.Build1.Tiles
local Mouse = Player:GetMouse()
local TargetedBlock

-- Border
local Border = Instance.new("SelectionBox")
Border.Parent = workspace
Border.LineThickness = .01
Border.Color3 = Color3.new(255,255,255)

-- Services
local RunService = game:GetService("RunService")

-- Block Data Handler
local BlockSize = Vector3.new(3,3,3)
local BlockMaterial = Enum.Material.Wood
local BlockColor = BrickColor.White()



-- Events
local PlaceBlock = game.ReplicatedStorage.PlaceBlock
local RemoveBlock = game.ReplicatedStorage.RemoveBlock

-- Make Border on Targeted Block
RunService.Heartbeat:Connect(function()
    local Target = Mouse.Target
    if Target then
        if Target.Parent == TileGrid then
            Border.Adornee = Target
            TargetedBlock = Target
        else
            Border.Adornee = nil
            TargetedBlock = nil
        end
    end
end)

-- Create Block on Click
Mouse.Button1Down:Connect(function()
    if TargetedBlock then
        if Mouse.TargetSurface == Enum.NormalId.Top then
            print("Attempt to place block")
            PlaceBlock:FireServer(BlockMaterial, BlockColor, (TargetedBlock.Position + Vector3.new(0,3,0)))
        end
    end
end)

The Server Script:

local Events = script.Parent

Events.PlaceBlock.OnServerEvent:Connect(function(player, Mat, Color, Position)
    print("Block Is Placed!")
    local NewBlock = Instance.new("Part")
    NewBlock.BrickColor = Color
    NewBlock.Material = Mat
    NewBlock.Size = Vector3.new(3,3,3)
    NewBlock.Position = Position
    NewBlock.Parent = workspace.Build1
    NewBlock.Anchored = true
end)

Also Try Putting The Server Script In ServerScriptService And Putting The Remote In Replicated Storage

Hope That This Helps!