subscribe to calendar over https

I'm trying to subscribe to a calendar that is only offered by an https connection.

Zoho never prompts me for a password, it just reports that it wasn't able to get the calendar. I also tried embedding my username / password for that site at 'https://username:password@xyz.com/calendar.ics' but that didn't work either.

Is there any way to subscribe to a calendar that is hosted on an https / ssl connection?

thanks