An observed side effect of adding an access control list to your Varnish Configuration file is that is can prevent the ability to download database back ups via the Cloud UI. This is because, while your access control list is limiting access to your sites, it is also limiting access to your Acquia default domain (example.prod.acquia-sites.com) which is required for database downloads to function.
A solution to this issue would be to either:
- add the IP addresses that you want to have the ability to download backups
- perform database downloads via the Cloud API