Undo button and redo button quit

My undo button is on the toolbar but is faint. View menu Can't undo is also
faint. I tried deleting and custom addition of the functions and they show
active until I close the custom window. Reloading or switching users does
not work. I saw a question on this and an answer about VBA or addon could be
affecting. What is VBA? I am not a programmer. I did import a xls file
that I received from an associate and startet working on that. Could that
have effected the main program?