Can't figure out why d() isn't working from tutorial code

[QuantumPie]

Hey! I'm trying to get started with developing my own addon and when I tried to use d() to print output I wasn't getting anything. After doing some digging I realized it won't print in initialized so I moved it to an event with no luck. I then directly copied the tutorial "Writing your first add-on" which also wouldn't print anything to the chat window. The addon is enabled and the description / author matches the manifest file. My file structure is

- DamageType/
- DamageType.lua
- DamageType.txt

My manifest file contains:

## Title: Damage Type Tracker
## Author: QuantumPie
## AddOnVersion: 001
## Version: 0.0.1
## APIVersion: 100030
## Description: Tracks the damage type of incoming damage so your CP can be optomized

DamageType.lua

And the lua file contains:

FooAddon = {}
 
FooAddon.name = "FooAddon"
 
 
-------------------------------------
-- Initialize the addon.
-------------------------------------
function FooAddon.OnAddOnLoaded(event, addonName)
    if addonName == FooAddon.name then
        FooAddon:Initialize()
    end
end
 
-------------------------------------
-- Load saved variables and register the event listeners.
-------------------------------------
function FooAddon:Initialize()
    FooAddon.inCombat = IsUnitInCombat("player")
    EVENT_MANAGER:RegisterForEvent(FooAddon.name, EVENT_PLAYER_COMBAT_STATE, FooAddon.OnPlayerCombatState)
end
 
function FooAddon.OnPlayerCombatState(_, inCombat)
    -- The ~= operator is "not equal to" in Lua.
    d("In event!")
    if inCombat ~= FooAddon.inCombat then
        FooAddon.inCombat = inCombat
   
        if inCombat then
            d("Entering combat.")
        else
            d("Exiting combat.")
        end
   
    end
end
 
EVENT_MANAGER:RegisterForEvent(FooAddon.name, EVENT_ADD_ON_LOADED, FooAddon.OnAddOnLoaded)

Which is a slightly modified version of the tutorial as I was troubleshooting. Is there a typo somewhere I am missing? I'd think that wouldn't be the case since it still didn't work when I had a direct copy of the code from the above tutorial.