Hi,
I just installed on a site for the first time this morning, added a Google calendar feed, added a shortcode to a page, ran in to this same issue, and found this thread. I started clicking around just to see what settings were what and saw the gzip disabled box checked and unchecked it. Things started working! Checked the box and things were still working. Not sure what happened there.
I did also notice when I tried another browser that wasn’t logged in it was giving a 403 error. I tracked this down to the iThemes Security plugin that was loaded. Turning it off made everything work properly. The incompatibility might be there.