For Surfly to work properly, we need to be able to establish a connection with your servers. If you have strict security settings in place (like a firewall, for instance) you might have to add the Surfly IP addresses to your whitelist.
Here's the list of our IP addresses: https://surfly.com/v2/servers/
You can also get this list by making an API call to our REST API: https://docs.surfly.com/rest.html#servers-servers-collection-get
This allows you to pin your Surfly sessions to a specific server region. You can also select a specific server on your Surfly dashboard at https://app.surfly.com/profile/options/session_functionality/