Try using the terminal and type
sudo apt-get install gnome-dictionary.
Most probably the software center isn't the problem but apt is. Therefore, the formerly mentioned command should fail and tell you why through an error message.
On a side note: people's answers tend to be much more helpful when you provide more information about your problem. In your case, "is not working" is way to general. Please explain further what happens. Are you seeing error messages? If so, what do they say? Can you install other software or is only installing gnome-dictionary the problem?