SSTP server setup/external certificate/linux client

I am trying to create an SSTP server on v7 using an external CA (not self-signed) certificate and I can get a server working with a windows client, but I cannot sort out how to get a Linux client to connect to the server.

There is probably a problem in the exchange of the certificates but I cannot figure out what is the problem. The frustrating thing is that the windows clients work.

Can someone help me to put together a configuration that works on both sides (M’tik and Linux) or possibly point me to a procedure?

Thanks for any help.