Hi Terry,
I think you need to use internal ip address, same as your SAP license server ip address.
If you can connect successful from your internal network, means that the connection setting is correct, and the certificate also correct, dont change to external ip.
And to connect from outside, you just need to find a method for connection, as I know like VPN client or public ip using secure port. For my case, I get help from their network expert cause I'm not a network guy yet.
Regards,
Muhamad