ZBrushCentral

Alt key not working in zbrush

I’m no sure what I did but, when I hold down the alt key to switch between zadd & zsub it no longer switches? Is there a place to reset zbrush settings? I’ve looked under Preferences for a ways to reset, but all I see that might work is Init zBrush. I’m reluctant to press this because I getting a warning stating that it will delete all document data, and I’m not certain what it means by all (all data of open document, all documents in projects folder, what?). So does anyone have an idea?