Avatar inspect script always returns "Instance"

I'm trying to make a game that allows players to inspect any other players' avatar by sitting in a specific seat and chatting their UserId or username, but when a user enters a username, the function always returns Instance, which is annoying. However, the UserId works. Here's my code:

-- client-side script
local Players=game:GetService("Players")
local Player=Players.LocalPlayer
local GuiService=game:GetService("GuiService")
local Rep=game:GetService("ReplicatedStorage")
repeat wait(0.1) until Player.Character
local h=Player.Character:WaitForChild("Humanoid")
GuiService:SetInspectMenuEnabled(false)
Player.Chatted:Connect(function(m)
    if h.Sit then
        if #string.split(m," ")==1 then
            if tonumber(m)~=nil then
                if h.SeatPart.Name=="AvatarInspectMenu" then
                    local id=tonumber(m)
                    GuiService:InspectPlayerFromUserId(id)
                end
            else
                if h.SeatPart.Name=="AvatarInspectMenu" then
                    local id=Rep.Idify:InvokeServer(m)
                    GuiService:InspectPlayerFromUserId(id)
                end
            end
        end
    end
end)

--server-side script
local cache={}
game:GetService("ReplicatedStorage").Idify.OnServerInvoke=function(n)
    if cache[n] then return cache[n] end
    local player=game.Players:FindFirstChild(n)
    if player then
        cache[n]=player.UserId
        return player.UserId
    end
    local id
    pcall(function ()
        id = game.Players:GetUserIdFromNameAsync(n)
    end)
    cache[n] = id
    return id
end

The client-side script works well, and I get an Avatar Inspect Menu for ROBLOX when I chat 1 in the chair, but when I chat ROBLOX in the chair, I get an Avatar Inspect Menu for Instance, or nil. Is there any possible way to fix this error?

The first argument passed to OnServerInvoke is the player that invoked the function, see OnServerInvoke

Since you are not interested in that, you can just ignore it by using a dummy underscore, like that:

game:GetService("ReplicatedStorage").Idify.OnServerInvoke=function(_, n)