Repository sync fails with the error 'RPM1004: Error retrieving metadata: A connection error occurred' on Satellite 6 server.

Issue

• While trying to sync repositories on Satellite, it fails withRPM1004: Error retrieving metadata: A connection error occurred.

• Red Hat Satellite 6 installed with proxy fails with below connection tests:

  #nc -v -w 5 cdn.redhat.com 443 
  Ncat: Version 6.40 ( http://nmap.org/ncat )
  Ncat: Connection timed out.
  
  #nc -v -w 5 subscription.rhsm.redhat.com 443 
  Ncat: Version 6.40 ( http://nmap.org/ncat )
  Ncat: Connection timed out.
  
  #nc -v -w 5 --proxy PROXY URL:PROXY PORT cdn.redhat.com 443 
  Ncat: Version 6.40 ( http://nmap.org/ncat )
  Ncat: Proxy returned status code 503.
  
  #nc -v -w 5 --proxy PROXY URL:PROXY PORT subscription.rhsm.redhat.com 443
  Ncat: Version 6.40 ( http://nmap.org/ncat )
  Ncat: Proxy returned status code 503.
  

• While trying to sync the repositories on Red Hat Satellite, below error has been observed in the Red Hat Satellite WebUI -> Monitor -> Tasks -> Synchronize repository Task :

  result: 
  error:
  code: RPM1004
  data:
    reason: Not Found
  description: 'Error retrieving metadata: Not Found'
  sub_errors: []