I spent a long time having full installed/patched/reinstalled but when starting the game and getting to the main menu it would remain on "Connecting to CONFLUX" without actually connecting. I had tried re-installing, port forwarding, spent hours on the phone with Ubisoft tech. Then weeks later I noticed that I had tried to delete a previous version of the game, I looked in my control panel-uninstall folder and I had a shell of a copy of HoMM VI left there, unable to uninstall it properly with it claiming I had files missing. This copy sat along side my new copy.
Solution: Uninstalled with a 3rd party program that uninstalls and also lets you scan for registry files and delete them. After deleting registry files referencing HoMM VI the shell of a copy was gone from the control panel uninstall list. I did a full reinstall of the game as well as ubi launcher and voila, connected to the conflux.
I hope this helps someone else out as this was extremely frustrating to me for an extended time.