I start having problems opening SAGE 50 Pro Canadian Edition Desktop program after activation of my new VPN provider Cyberghost. I was getting timeouts and DCM connection errors when the VPN was ON. As soon as I put it OFF, all problems went away. I try my other VPN provider Bitdefender and had no problems when it was ON. After a week of exchanging emails with Cyberghost support team and getting mostly generic replies from rebooting my PC to reinstalling the TAP adapter (all was for nothing) I finally got an answer from the top level tech support. Apparently when the Cyberghost VPN is ON, it blocks most of the ports (for security reasons refering to this article torrentfreak.com/.../ ) including the ports 13531 and 13540-13579. The only ports that are open when connected to the VPN are the following: 443, 1194, 8080, 8081, 500, 4500, 8443, and GRE.
Even if I explicitly open the DCM ports in the firewall, it will have no effect because the VPN overrides the firewall rules, and I can not change those rules. 

Is there a way to use the GRE ports for DCM? If not, what is the solution? For now I just switch off the Cyberghost VPN when I need to work with SAGE 50.