attempt to index local 'char' (a nil value) why is this happening?

The reason your code is not working as you are not sending over the "Char" as an argument when running your custom funtion. Thats an easy fix. Use this:

local player = game.Players.LocalPlayer
local plot

local function MoveChar(char)
    wait(0.1)

    char:SetPrimaryPartCFrame(CFrame.new(plot.Plot.Spawn.CFrame.X,plot.Plot.Spawn.CFrame.Y + 5, plot.Plot.Spawn.CFrame.Z))
end

player.CharacterAdded:Connect(function(char)
    for i,v in pairs(workspace.Plots:GetChildren()) do
        if v then
            if v.Plot.Owner.Value == player then
                plot = v

                MoveChar(char)
                break
            end
        end
    end

end)

dosent player.CharacterAdded only fire on the server? if not my bad