As a test, If you try to reach directly the following links from any browser on your server:
It is most likely both will require to add credentials to the Proxy server:
If you add the proper credentials, it should download the files just fine.
The proper way to resolve this issue is:
1. Add the proper exclusion to your Proxy/Firewall rules
2. OR add the valid credentials for Proxy access under SIM:
a) SIM>Settings>Proxy Settings>Change>Add the requested information. Save changes and relaunch SIM.