Trouble with registering a client server

DSC
1 
The attempt to register Dsc Agent with AgentId F300E97F-CB62-11E5-80BC-D5B83049D147 with the server
https://pullserver.strongcobra.com/PullServer.svc/Nodes(AgentId='F300E97F-CB62-11E5-80BC-D5B83049D147') returned
unexpected response code Forbidden.

My PullServer has web.config with “Nodes” in appsettings

[DscLocalConfigurationManager()]
Configuration Register_SC_DC1
{
    Node localhost
    {
        Settings {
            RefreshFrequencyMins = 30;
            RefreshMode = "PULL";
            RebootNodeIfNeeded = $true;
        }

        ConfigurationRepositoryWeb ConfigurationManager {
            ServerURL = "https://PullServer.MyDscProject.com/PullServer.svc"
            RegistrationKey = "24852231-2da5-4c08-a683-e10a03a8bc7b"  
            ConfigurationNames = @("mdp-dc1")
        }
    }     
}


Register_SC_DC1 -outputpath C:\users\Public\dsc
Set-DscLocalConfigurationManager -ComputerName localhost -Path C:\users\Public\dsc -verbose