Copy to calendar no longer an option in Outlook 2016 calendar where I have two different calendars

I recently reinstalled Windows 10 and Office 365.

I have 2 email accounts with 2 calendars in Outlook, one calendar being my primary and the other a secondary calander.
Previously I was able to copy events in my secondary calendar to my primary calendar using the 'Copy to my calendar' button in Outlook.
I can no longer find this button so am wondering how I copy events from one calendar to the other?

Also, as a matter of interest, my one account is now a Microsoft Exchange account, the other an Outlook Active Sync account when both were previously Active Sync accounts.  Would this have anythin to do with the problem I now have?