[Fizzlemizz]

In both the code files you have

local db = {}

This is creating distinctly different db variables.

In the main file add db to your ns table and get it from there in the ChatCommands.lua file.

Or use MapNotesMiniButton.db in the ChatCommands.lua file, whichever db is the right one and is available in both files either via a global or the ns table.

A quick look further and in the main file you're creating

local db = {}

and then throwing it away in PLAYER_LOGIN and replacing it with

db = self.db.profile

Where self is Addon. Which means Addon should be added to your ns table and in ChatCommands use:

local db = NS.Addon.db

or give the frame a name and use that.