Peer Cache doesn't take effect on one primary site

Hi guys ,

Our environment is one CAS with three primary sites (SCCM 2012 R2 1710). All clients connect to one of three primary sites according to their boundary groups.

Now we fond a strange thing that all clients which connect to one specific primary sites doesn't take effect on Peer Caching.But the other clients which connected to other two primary sites take effect on Peer Caching.

Does anyone can give some clues ? Thanks in advance.

My Peer Cache Policy

PowerShell to get Peer Cache apply status

 Get-WmiObject -ComputerName localhost -Namespace "root\ccm\policy\machine\RequestedConfig" -Class "CCM_SuperPeerClientConfig"