I do not see a category selector anywhere in the DOM. (I think I understand what I'm looking for, but I'm a novice at this.)
Also, in addition to not being able to select a category, the previous calendars (I had 3 in addition to Default) are not shown in manage calendars. And, none of the previous events are available in Manage Events.
When I attempt to view the calendar in the front end, nothing but a dot in the upper left cornet shows (both in Safari and Firefox) - no calendar layout (I've never used anything but the default.