Hi.
I have the same problem after updating the Tribe plugins. My theme is pretty old, but it was working fine before the upgrade. Rather than spend hours troubleshooting JQuery and/or theme conflicts, my super-quick patch is to display the categories again with a simple CSS override. Just add this to your theme’s style.css file.
#event-categories.tribe-hide{
display: block;
}
Hope it works for someone.