Hi,
I made some tests.
When I set URLfilter to www.skype.com, the ALLOW, MONITOR action will block it because the Category is set to block: Category: Internet Telephony
The reason is because the URL filter has actions:
Allow - Any attempt to access a URL that matches a URL pattern with an allow action is permitted. The traffic is passed to the remaining antivirus proxy operations,
including FortiGuard Web Filter, web content filter, web script filters, and antivirus scanning.
Monitor - Traffic to, and reply traffic from, sites matching a URL pattern with a monitor be allowed through
in the same way as the “Allow†action. The difference with the Monitor action being that a
log message will be generated each time a matching traffic session is established. The requests will also be subject to all other UTM inspections that would normally be applied to the traffic.
So it means, that you have to enable the www.skype.com by recategorizing the site into custom category - It worked for me.
The URL filter is usable only if you want to block some site or if you have trusted site you can enable it with Exempt action.