Using Classic Outlook on Windows for personal email, calendar, and contact management
Same. I noticed this recently as I used to be able to copy items on shared calendars but now get this same error message.
Outlook version:
Microsoft® Outlook® for Microsoft 365 MSO (Version 2206 Build 16.0.15330.20306) 32-bit
Copying and pasting on my individual named calendar also works fine. It's only on the shared calendar and I am an owner on the shared calendar. Same with my coworker who is also an owner on the shared calendar.