Hovering over player does not work?

So this likes to appear the billboardgui over the baseplate and it won't go away. I don't get this. What am I doing wrong? The point is, hovering over a player should show their FirstName and Surname according to a DataStore that is always set if they're in-game and past the introduction where you pick your name. It literally just doesn't work at all properly and it's unexplainable. In starterplayerscripts:

local plr = game.Players.LocalPlayer
local Mouse = plr:GetMouse()
while wait(0.5) do
    if Mouse.Target ~= nil then
        if Mouse.Target.Parent:FindFirstChild("Humanoid") then
        plr.PlayerGui.BillboardGui.Enabled = true
            plr.PlayerGui.BillboardGui.Adornee = Mouse.Target.Head
            plr.PlayerGui.BillboardGui.FirstName.Text = game.ReplicatedStorage.getfirstname:InvokeServer(game.Players:GetPlayerFromCharacter(Mouse.Target.Parent))
            plr.PlayerGui.BillboardGui.Surname.Text = game.ReplicatedStorage.getsurname:InvokeServer(game.Players:GetPlayerFromCharacter(Mouse.Target.Parent))
        else
            plr.PlayerGui.BillboardGui.Enabled = false
            plr.PlayerGui.BillboardGui.Adornee = nil
            plr.PlayerGui.BillboardGui.FirstName.Text = "FirstName"
            plr.PlayerGui.BillboardGui.Surname.Text = "Surname"
        end
    end
end

in serverscriptservice:

function game.ReplicatedStorage.getfirstname.OnServerInvoke(plr)
    return game:GetService("DataStoreService"):GetDataStore("FirstName_1"):GetAsync("user_"..plr.userId)
end
function game.ReplicatedStorage.getsurname.OnServerInvoke(plr)
    return game:GetService("DataStoreService"):GetDataStore("Surname_1"):GetAsync("user_"..plr.userId)
end

Please help!