Calendar not opening

[Murray P Robertson]

When I click on the Calendar app there's a brief flicker then nothing I cannot open it

 

[Trouble]

With only that information to go on, My suggestion would be to ......
Right click the start button and choose Run and in the run dialog box type
ms-settings:windowsupdate
hit enter or click OK
See if there are any pending reboots or updates.

 

[Murray P Robertson]

Thanks. I had tried that. Have now reinstalled Windows 10 and it's back to normal