[FE] Why are my Players Gui's not showing up on the Server?

[Filtering Enabled] I put the Gui's in the StarterGui. It gives the gui's to the player, but when i try to call one of the Gui's from the Server Script(that is in the ServerScriptStorage) it says that the Gui doesnt exist.

Example Script- (In Server Script Service)

player = game.Players.ScriptingBook
local CurrentCash = player.PlayerGui.Cash.Value

Error: Cash is not a valid member of PlayerGui

The server can not see a client's PlayerGui with filtering enabled on. My suggestion is to use remote events to send the value from the client to the server, or just store it on the server and fire it to the client when needed (again using remote events.)