FAQ: How to reset (trash) preferences in After Effects?
Here is how you can reset the preferences:
Press Alt (Windows) or Option (Mac OS) while launching After Effects. You can release the Alt or Option key when the splash screen appears.
To reset preferences and plug-in cache at the same time, hold down Control-Shift-Alt (Windows) or Command-Shift-Option (Mac OS) while the application is starting. Release the keys when the splash screen appears.