ZBrushCentral

Alt Key Funtions not working! Please help!!!

I have a pproblem. not of the functions that the ALT key is supposed to activate work. Example: Sculpting on a model with the standard brush with zadd activated, hit ALT key to activate zsub and begin to sculpt, nothing happens. The curser changes from a plus to a minus but the model in not effected. Same with masking, zspheres, etc… Any ideas?

Please Help!!!

CF