Can't change dimension in solidworks Drawing

Hi,

I suddenly can't use the smart dimension on the document I'm working on. Whenever I make a sketch, the dimension cannot be changed to the number I entered.

See on attached pic: The blue is line I draw, then i try to modify the dimension but the line keep in its dimension.

I tried to draw in a new sheet or document, it works fine. Why is this happened? Please help, thank you.