The Netop applications have problems when going through the web filter.
Add the netop.com domain to a white-list policy. This can be done by adding the domain to an existing category that is being white-listed or by creating a new custom category and adding netop.com to the category. Then create a white-list policy in "Guardian - web filter - manage policies" and add the new custom category in the "what" step.
If Smoothwall is also used as firewall, outgoing traffic needs to be allowed on TCP port 6502 to these IPS:
- EU: 126.96.36.199 and 188.8.131.52
- US: 184.108.40.206 and 220.127.116.11
Netop knowledge base has a good article located here.