Need Help with 3115cn

This morning my 3115cn printer won't let me print out of tray 1 and gives me this message "Illegal Settings.  This is unavailable custom sized selected."  I do not know how to fix this problem.  Tray 2 prints fine, but I cannot tray 1 to function.  Do I need to do a factory reset of the printer?  If so, how do I do that?  Thanks for any help you can give me!