First, verify that Silverlight has been enabled on Internet Explorer.  To do this:
  1. Open Internet Explorer, select the Tools button , and then select Manage add-ons.
  2. Under Show, select All add-ons.
  3. Select the add-on, Enable, and then select Close.
What if Silverlight is in the Run without permission section?

If Silverlight is only showing in the Run without permission section, then this is a permissions issue.  To remedy this:
  1. Browse to C:\Program Files (x86)\Microsoft Silverlight
  2. To view the security permissions: Right-click, Properties, Security
  3. Then change security permissions by adding yourself as a user with FULL control of the folder and the sub-folder and files.