Trying to scan my hosts for updates and getting:
You have ports blocked for update manager, hence the download of patches or updates is failing.
If you have a proxy then provide the address @ download tab under "Configuration" tab of update manager.
When you also perform a scan try selecting only patches and then check if the download completes or fails. Perform the vice versa for updates.
please see the network configurations in your vSphere and make sure that you got internet on that machine. If you have any proxy server then put the proxy address your browser. Then may help to update your system.
Best place to start is your the DNS settings on your ESXi Hosts.
Verify these are correct, then enter any proxy details in the 'Admin View' of Update Manager.