This is a new problem. VM 2019.06 on Windows 10 Pro 10.0.18362 Build 18362.
I have several calendars one of which is Bill Dates which is usually hidden (no check mark next to name). When I double click on a date in month view or click on New Event the dialog box opens but it's for the calendar Bill Dates and a check mark is now in the box next to the name.
Prior to this just starting I'd double click on date in month calendar and the dialog box would open with the correct calendar, Google Calendar.
There was a recent Windows 10 update so I don't know if this was the cause or if there is something else going on.
Any suggestions?