Failure downloading upgrade list: received invalid update manifest response

Scenario:  When upgrading Cisco Email Security Appliances, you may run into the following error when upgrading from one OS to the next:

Error:  Failure downloading upgrade list: received invalid update manifest response

Solution: Check where the server is pointing to for pulling the list of updates:

Run the following commands via the CLI:

• Updateconfig
• dynamichost
• update-manifests.sco.cisco.com:443
• Commit