I have seen so many times SCCM client status is not approved or N/A after you push client to that particular server. If you install sccm client manually in this server also same story only.
So where we need to look in to this to get client status approved and client assigned Yes.
1 ) Open these ports in firewall
80, 445 ,443 ,135 , 8530 and 8531
2)Check the ip subnets are in sites boundaries.
3) check the sms agent host, BITS and WMI services are running.
If the bove settings are configured then go to configuration manager console and right click from collection and update membership collection then refresh. Now the client status should be Yes and Assigned