means that your client cannot find a DNS server that knows the location of your domain controller. You can see which DNS records specifically it cannot find if you click the details button when the error takes place.
Make sure that your client is using the correct DNS server IP address before you try to join it to the Windows domain. Also verify that the DNS server is joined to the domain and contains the necessary records for the domain controller. After you do that try to join the client to the Windows domain.Tags: AD server