In an recent issue, while trying to upload a new Windows Azure Package (CSPKG & CSCFG) to Windows Azure Management Portal., cause problems. The same steps were working fine forever however suddenly the following error occurred:

 8:43:09 PM - Preparing...
8:43:09 PM - Connecting...
8:43:10 PM - There was no endpoint listening at https://management.core.windows.net/<Subscription_GUID>/services/hostedservices/datacenter-1/certificates that could accept the message. This is often caused by an incorrect address or SOAP action. See InnerException, if present, for more details.
8:43:10 PM - Deployment failed


Based on the error description, creating & uploading new certificate did not solve the problem and trying  to go to the next screen return following error message:

 There was no endpoint listening at https://management.core.windows.net/<Subscription_ID>/services/hostedservices that could accept the message. This is often caused by an incorrect address or SOAP action. See InnerException, if present, for more details.
Unable to connect to the remote server
No connection could be made because the target machine actively refused it 127.0.0.1:8888

Investigation and Solution:

After some investigate the real culprit appeared as Proxy Server settings in the development machine. The development machine was using a proxy server which was causing this problem. So the problem  was related with Proxy Server, which was acting in middle between computer and Windows Azure Management Portal. After removing Proxy settings and following the same steps, the problem was resolved.