Problem with gpo and the Security Zone´s addition.

Hello,

  I have configured a GPO to set a url to the security zone. The steps I followed are:

1.- Open GPMC

2.- User configuration-->Administrative Template-->Windows component-->Internet Explorer-->IE Control Panel-->Security Page-->Site to Zone Assigment List and I added the url.  
On the pc client I run "gpupdate /force" to implement the policy, the problem is that in all PC that was applied, the user can not add others  url, because this option appears not available to do this, it kept gray.

What are doing wrong?  Could you help me?

acc

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