Ah, the problem is with the change to disable the wiki markup.
Looking at your console output (F12 on most browser) this error appears
ko-calendar.js?ver=4.1:269 Uncaught ReferenceError: entryDesc is not defined
ko-calendar.js?ver=4.1:269 (anonymous function)
It is due to to line 269 of ko-calendar.js
bodyDiv.innerHTML = entryDesc;
Which I assume is due to a bad merge with an older version of the plugin in your revision control OR the instruction in the FAQ about how to disable the wiki markup formatting are now wrong.
They should now read something like the following. The key is to remove the function call to Wiki.toHtml() and leave everything inside it.
If you wish to remove this transformation simply replace the following line in ko-calendar.js
bodyDiv.innerHTML = Wiky.toHtml(entry.description != null ? entry.description : “”);
With
bodyDiv.innerHTML = entry.description != null ? entry.description : “”;
I will update the FAQ (and maybe the next version of the plugin will just make this an option so you don’t have to change it.