I need some help trouble-shooting the creating a new Calendar and using the feature "Synchronize appointments from remote calendar".

When I try to add the URL for the "Synchronize appointments from remote calendar", Zimbra responds with the error: "The following URL is not currently unreachable".

I already have 6 other calendars created which synchronise from the same base URL (same host name but different path to ics), however I just cannot add any new calendars. We recently moved the Apache server hosting the calendars onto the Zimbra server so I expect it is something to do with that recent change that is the problem. It is weird that the old calendars still work though, just cannot create new ones.

The remote calendar we want to access is located on the same Linux server, but a different Apache installation. The URL used is accessible from my workstation and from the command line on the Linux server hosting Zimbra.

Does anyone know if there are Zimbra calendar logs I can view to find out what the actual error is?

Thanks in advance!