Getting the following error; "Host: <hostname> An error occurred  in communications Reflection SSL/TLS could not establish an encrypted connection" when attempting a host mainframe connection over a VPN (Virtual Private Network). 

In this particular situation, the cause of the issue was that the VPN Firewall was doing SSL encryption of all the inbound traffic from the client workstation. This was affecting applications like Reflection Desktop.  During the TLS Handshake, the VPN Firewall  was presenting the VPN Firewall certificate where Reflection Desktop  was expecting the host mainframe certificate for further validation. Since the wrong certificate was presented, the TLS Handshake was terminated as this point, which in turn caused the error to occur in the Reflection Desktop software. 

Full article: https://portal.microfocus.com/s/article/KM000016539