Can't pass objects from client-server?

Hello there,

I am working on my game right now, and just started working on the engine this week. I have a function that creates an object on the server, and then returns that object. It seems to work fine when I am returning the object from the server to the client, however, the part does not get returned when the situation is flipped around. I tried to return a part made on the client, but it wouldn't return the object and just kept returning nil.

So I am wondering if this is because of a roblox issue and I need to find an alternative to accomplish this task, or is it just something wrong with my code. I will post the code below so you can analyze exactly what I mean.

-- Server - Client Function --
local rs = game:GetService("ReplicatedStorage")
local folder = rs:WaitForChild("Instance Work")
local instance_func = folder:WaitForChild("Instance")

------------------------------------------------------  
    -- Creates a part on the server --

local function instance(plr, obj, props)
    local object = Instance.new(obj)

    for prop, value in next, props do
        if prop == 'Parent' then
            value = return_obj_from_string(value)
        end

        object[prop] = value
    end

    if object then return object end
end

instance_func.OnServerInvoke = instance

    -- Creates a part on the server --
------------------------------------------------------

The above will create an object on the server and then successfully return that object to the client.

-- Client - Server Function --
local rs = game:GetService("ReplicatedStorage")
local folder = rs:WaitForChild("Instance Work")
local instance_func = folder:WaitForChild("Instance")
------------------------------------------------------  
    -- Creates a part on the client --

local function instance(obj, props)
    local object = Instance.new(obj)

    for prop, value in next, props do
        if prop == 'Parent' then
            value = return_obj_from_string(value)
        end

        object[prop] = value
    end

    if object then return object end
end

instance_func.OnClientInvoke = instance

    -- Creates a part on the client --
------------------------------------------------------

The above creates an object on the client, however, it fails to return the object to the server.

The code below is how I made the call to the client from the server and how it failed to return the part.

-- Script inside Click Detector, which is inside a part and meant to activate the client function upon clicking the part --
local detector = script.Parent;
local rs = game:GetService("ReplicatedStorage");
local instance_folder = rs:WaitForChild("Instance Work")
local instance = instance_folder:WaitForChild("Instance")

detector.MouseClick:Connect(function(plr)
    local char = plr.Character or plr.CharacterAdded:Wait();
    local root = char:WaitForChild("HumanoidRootPart");
    local props = {
        ['BrickColor'] = BrickColor:random();
        ['Transparency'] = math.random();
        ['Anchored'] = true;
        ['CanCollide'] = false;
        ['Material'] = Enum.Material.Neon;
        ['CFrame'] = root.CFrame;
        ['Parent'] = workspace;
        ['Name'] = 'Innovation';
    }
    print("It is:", instance:InvokeClient(plr, 'Part', props)) -- Prints "It is: nil"
end)

Thank you for any help and hope you have a nice day/night.

Best regards,

IdealistDeveloper