The 2Share Essentials requires an active internet connection for 'workspace sharing' and software updates. Workspace sharing function is making use of SES service from Microsoft Azure and uses HTTPS port 443. Also the 'Software update mechanism' will use HTTPS on port 443
Additional to that you need to make sure that HTTP port 80 is open for internet access.
Voila port configuration is a bit different, and complete setup can be found here
|Workspaces sharing via Email||Port 443|
|Software update of the 2Share Essentials||Port 443|
|Checking for services||Port 80|