Start Button, Cortana and Calendar App not working in Windows 10. How can I get them working?

[Windows Central Question]

Start Button, Cortana and Calendar App not working in windows 10

I upgraded to win 10 from Win7 professional, at initial days all are fine, after some days Start Button, Cortana and Calendar App not working in task bar.
I installed all windows update but issue not fixed. Please suggest the fix. Thanks in advance.

Regards,
Austin Jose