Applying Group Policy to an Entire Site

I am trying to Apply group Policy to An Entire Site. At the moment I have 1 Top level Domain – Domain.com and many sub Domains – sub1.domain.com, sub2.domain.com ect. I want to enfore a group Policy to all users and computers in every domain. To do this I’ve set a group policy up from the Site Level. Problem is the policy applys to servers but not workstations. I have set No Overide on the policy and checked that there is no GPO under it with Block Inherritance. When I do a GPResult from a workstaion it doesn’t even list the GPO I have applied from the Site Level. Any help to find out why this is happening would be appretiated. Thankyou