HELP! site gets blocked, how to unblock?

I have a customer that works with Firefox and we think CIS has blocked a part of this site. The site is https://www.ziggo.nl/ and when she goes to her web-mail on https://webmail2.ziggo.nl/ witch is java based it will not load no more. She thinks that there was a pop-up or something from CIS but she does not remember.

Where can I check in CIS if the firewall or D+ blocks this site and un-block it.

firewall and d+ events

Need some more input.

You mention, I think 2 places?, and how do I tell CIS that a site must be unblocked?

Is Comodo DNS enabled?

If the site is blocked by CIS it should be in Blocked Zones (Firewall → Network Security).