I've seen tons of posts with totally bewildered (contacts and calendar
issues) "MVP's" only making matters MUCH worse.  Some MVP's need to
actually try some things and always keep in mind "Occam's Razor."
You're trying way too dang too hard, people!

The real answer to fixing the Calendar button if you click it and it
gives you an empty view, is to go to the "Go" menu and then select
"Folder List" and then click on "Calendar" in the list.  Now,
right-click on the Calendar "folder" in the list and choose "Add to My
Calendar" and then when you click the button at the bottom of the Nav
Pane, it will actually open your calendar.

Lord only knows why/how Outlook decided to stop doing it right in the
first place...bloatware tends to be buggy like that.