Currently, there is a bug with the launcher that will prevent you from changing your game folder location, so you have to manually fix that for now.
Go to your start menu and type run
Open this program, it will show a text box, in this text box type %localappdata% then press the enter key
It will open a folder in the explorer. Now locate the folder called plutonium
Right-click and delete that folder. Now when you launch the launcher again the setup button will be visible allowing you re-select your game folder.