I am having the exact same issues. I have been using this trainer since Gathering Storm was released, and have always had success with its functions. However, today, for some reason, the Unit Can Level Up box will not hold a numerical value. When the TAB key is depressed, the value resets itself to zero. I am not quite sure what is different, but I am confident our illustrious benefactors will figure it out in due time.
literally means you are not starting a game or loading a game that has Gathering Storm DLC/Expansion enabled. It's literally in the instructions and multiple areas here that you have to have it enabled.
you didn't read the instructions?
Do I need to have both installed or only 1 for the trainer to work?