The pop up window doesn't show up when I double click. It only adds the default track. How do I get it back?
In absence of following information in your question such as Music Maker version and Windows's operating system you reset the program to its default settings File-Settings-Reset. (may be it help you). In case of RESET if you have changed settings that will be lost therefore, before resetting make a memo of that.
Can you see BeatBox 2 among other synthesizers? It seems you want to open the BeatBox 2.
Other than above if you deleted something, computer registry entries got corrupted etc such problem could occur. To run software and computer smoothly always keep update: Operating system, Software, Browser, Adobe flash Player, Java and computer drivers.
nihon94