If you are getting a "Your session has timed out due to inactivity" message on a green screen like this:
This only means that the web page in the background timed out. This will not impact your Hosted Desktop session in Citrix, and will not cause your session to close.
To reach the Hosted Desktop, you will log in to the connect.onenet.co.nz web page, and then from there open up your Hosted Desktop session inside Citrix. The web page will still sit in the background while you are using the Hosted Desktop, and the web page will time out after 20 minutes. The time out will always happen, but you will only see this 'time out' message sitting on the web page after the Hosted Desktop has been closed.