How strange, sorry to hear you’re hitting this.
The calendar isn’t truly empty in these situations – the events are present, they just aren’t visible. Perhaps adding the following line of CSS would help here:
#tribe-events .tribe-events-calendar h3 { opacity: 1 }
(The basic problem is that opacity of numerous elements is set to zero.)
Other notes:
A special CSS box that applies to the calendar would be very very helpful.
Though we don’t provide that you can set up a custom tribe-events.css stylesheet for rules like the above one.
Does that help?