I think it's an "Add-On" and not a "Module" in Roll20 Terminology. This means you Add it to your game in a different place. It's not in the place you were expecting. Create a game first, it can be a blank game with no module. Or it can be your existing game if you're already running one. On the Game Details Page (the webpage you see as GM before clicking Launch Game, the page that Launch Game is on).... Scroll down to the middle/bottom and look for "Game Addons". Click that and use the Drop-down menu to select the product that you bought and press Add To Game. Yes it's confusing, but it's fast and easy once you spot it
