AnyConnect on Windows fails to connect to Cisco ASA but openconnect gui will connect

[D. Scott Shepard]

We have a Cisco 5516-X ASA with an SSL VPN configured. We're
experiencing very strange behavior with this VPN, as follows:

1. AnyConnect client (v. 4.8/4.9) on Windows 10 has trouble
connecting, often requiring 6-8 attempts. Most often the client says
"Could not connect to server. Verify Internet connectivity and server
address." (Internet is good, and I can ping to and tracert to server)

2. AnyConnect client on Linux connects mostly without any problem.

3. Openconnect GUI on Windows connects with almost never a problem.
The couple of times it didn't connect, the log said the "server
actively refused the connection."

We would just use Openconnect, but we need the connect before login
and network manager features of AnyConnect.

I have spent days Googling this, but nothing has been "the fix."

What is Openconnect doing differently than AnyConnect (especially on
Windows 10)? and,

How can I fix it?

I realize this mailing list is for issues with Openconnect, but I've
run out of other places to look.

Thanks