When in the setup wizard, if the update step fails (connection unexpectly closed), it usually means that in front of your pbxware box there is a system that filters network traffic on port 80. This port is used by pbxware to perform firmware update. In order to resolve this issue:

• Login to the system shell as a root user
• Edit all 'home/serves/(httpd,pbxware,sitemanager)/sh/update' files.

• Where it says: 'pw-updates.bicomsystems.com:80' change port '80' to port '8730'
• Save files

• Navigate to the setup wizard window and refresh it by pressing 'CTRL + F5'