Hey there dgordo,
Taking another look at If you can’t add iCloud Mail, Contacts, or Calendars to Outlook, you'll want to utilize iCloud for Windows instead of the method you used to add your calendar:
- "Check that your PC meets the iCloud system requirements and is connected to the internet.
- Download iCloud for Windows and sign in with your Apple ID. If you have multiple Apple IDs that you use with iCloud, check that you're logged in to iCloud for Windows with the same account that you use on your other devices."
"If you don't see recent changes, or iCloud for Windows doesn't support your version of Outlook, learn what to do.
If you don't see recent changes made in Outlook
If you recently made changes in Outlook that aren't updating on your other devices, or changes on your other devices that aren't updating in Outlook, select Refresh in Outlook.
If the installed version of Outlook isn't supported
If you receive an error that says the Installed version of Outlook is not supported by iCloud, uninstall the version of Office that you got from the Windows store.
Then follow these steps to install Office 365"
Have a good one!