ICal showing as plain text

There was another post, with the same problem but no resolution was given.

I’ve tried the Rt demo site, and it works fine.

My system RT 3.8.8 show it in plain text.
I compared the URLs between the Demo site and my site and they seem
identical, so I’m guessing it’s an apache config issue.
I check the mime-types in apache and the text/calendar type resolves to ics.

I double checked my apache config and it appears consistent with all of the
instructions I found.

Did anyone solve this?