New Event/Tasks doesn't go in after Save and Close
Windows 10/Thunderbird 78.3.3:
After finally being able to create a Calendar "database", now putting anything into it doesn't work. I followed exactly this link's instructions: https://support.mozilla.org/en-US/kb/creating-a-new-event-or-task
"Save and close" does nothing. I pushed it, and it (the button) is still available. And no task or event goes in, and nothing is reminded. The attached image is AFTER I pressed "Save and Close", you will notice that it is still available, and that the calendar in the background shows nothing. No errors, no warnings, nothing done. Even after closing popup window, nothing in main window appears.