On my Windows 10 (virtual machine running on my Mac) it always says,
"Could not connect to server. Please verify Internet connectivity and server address."
I have users running standalone Windows 10 also have the same problem.
But the Anyconnect installed on my Mac High Sierra has no problem. Any reason why it happens like that? Our organization is running ASA 5516. Not sure if there is anything that needs to configure at the firewall.