Note: This question is part of a series of questions that present the same scenario.

Linking a GPO to Site1 causes that GPO ' s settings to apply to computers that are members of Site1, not to the client computers in the new branch office, which are not part of Site1 at all. GPO scope (whether a GPO is linked to a site, domain, or OU) only controls which already-existing site or directory container ' s computers receive the policy; it cannot make a computer become a member of that site. Site membership continues to be computed solely from the client ' s IP address against the subnet-to-site mappings defined in Active Directory Sites and Services. The Try Next Closest Site setting itself only affects what a client does when no domain controller exists in its own site — it tells the client to prefer the closest site by site-link cost rather than picking an arbitrary reachable site — but it never overrides or replaces the initial site-lookup step. Because the branch office clients are not members of Site1, and this solution does nothing to change that, applying the policy to Site1 has no effect on the branch clients whatsoever. The goal requires making the branch subnet a member of Site1 (or otherwise altering how the branch clients resolve their site), which this solution does not do, so it fails to meet the stated goal.