Uploading packages in MODx Revolution

I can upload packages in MODx Revo. An error occurred while connecting to the Provider: MODX received a blank response from the provider. Please double check your service URL and make sure the provider is a valid provider.

cURL enabled amd I can ping MODX Web Content Management System and Platform.

Is there anybody who had such a problem and knows the cure? I will appreciate any advice.

Thank you

[Gianluca]

Have you tried to unblock your server to server connections? They are limiyed by default to a whitelist of domains.