iCal won't subscribe to zoho private calendar address???

iCal won't subscribe to zoho private calendar address???

I keep trying to go to my iCal calendar and subscribe to my zoho calendar by it says it isn't valid.  I get this error every time.  I have copied my private address from zoho and then when I go to my iCal and subscribe it gives me an an error message.  My google calendar worked okay.  What is the problem?

The data downloaded from http://calendar.zoho.com (I removed my private address) isn’t valid.