Undo Preferences?

[Gracie5FCE]

Hello!! My "Undo" button is not working (won't work in edit > undo either). I think I turned it off by accident (if that's even possible). How do I turn it back on? Thoughts? 

[Peter Spier · Accepted solution]

Not something you can turn off. Reset the prefs: Reset InDesign Preferences and Other Troubleshooting