Edited events don't save

[Eroppo]

I'm new to Linux, so may be doing something wrong: connected Outlook calendar for using in both W10 and Ubuntu (depending on what OS is loaded), but can't change any event (reassign to another date/time): after modifying and pressing 'save and close' the event window is closed, evend is displayed as moved to the new date, but the calendar itself switching to read-only mode. After closing/reopening Thunderbird the event is reversed to the state before editing...