Unable to call a function

[Kronn8]

I feel like I'm taking crazy pills.
I'm simply trying to call a function using a slash command, but I keep getting this error when I input a command.

Entering "/fmi show" in the chat window results in this error:

user:/AddOns/FMI/FMI.lua:41: function expected instead of nil
stack traceback:
	user:/AddOns/FMI/FMI.lua:41: in function 'FMI.Command'
	EsoUI/Ingame/SlashCommands/SlashCommands_Shared.lua:71: in function 'DoCommand'
	EsoUI/Ingame/ChatSystem/SharedChatSystem.lua:1813: in function 'SharedChatSystem:SubmitTextEntry'
	EsoUI/Ingame/ChatSystem/SharedChatSystem.lua:2531: in function 'ZO_ChatTextEntry_Execute'
	ZO_ChatWindowTextEntryEditBox_Enter:3: in function '(main chunk)'
	(tail call): ?
	(tail call): ?

Below is my current lua file. I've marked the problem line in red.

----- Free My Inventory

----- Declare Core Data/Objects
FMI={}


---------------------------------Output --------------------


-------------------------------- Initialize------------------------------------

function FMI.Initialize(eventCode, addOnName)
	if(addOnName == "FMI") then
		EVENT_MANAGER:UnregisterForEvent("FMI", EVENT_ADD_ON_LOADED)
	end
end


-------------------------------- Functions------------------------------------

function FMI.showWindow()
	FMI:SetHidden(false)
	return
end

function FMI.hideWindow()
	FMI:SetHidden(true)
	return
end

function FMI.Command(options)
	if options == nil or options == "" then
		d("Please add options \"show\" or \"hide\".")
		return
	end

	cmd=string.lower(options)

	if cmd == "show" then
		d("Trying to show window...")  -- This prints successfully in the chat window.
		FMI.showWindow() --ERROR: function expected instead of nil
	elseif cmd == "hide" then
		d("Trying to hide window...")
		FMI.hideWindow()
	end
	return
end


------------------------------------------ Event Handling ----------------------------------------------

SLASH_COMMANDS["/fmi"] = FMI.Command
EVENT_MANAGER:RegisterForEvent("FMI", EVENT_ADD_ON_LOADED, FMI.Initialize)

I'm at my wit's end here. I copied the aforementioned code from an existing add-on. That add-on works, so I cannot for the life of me figure out why my copy isn't working.

Thank you in advance for any help!