The Server Responded with an error. Access to account "icloud" is not permitted. The server responded: "403" to operation CallDAVAccountRefreshQueueableOperation.

Hello MR258,

We're glad you thought to ask Apple Support Communities about the issue you're having with your iCloud calendar not syncing and showing the alert. See if the steps in the following guide help: If your iCloud Contacts, Calendars, or Reminders won’t sync

Let us know how it goes.

Take care.

I am also having the exact same issue, but I am experiencing this on macOS Monterey (12.1) as well. It is generally NOT affecting my iOS devices, but calendars on my MacBook Air and also within the iCloud app (web version) fail. Tried 3 different browsers, and 2 different computers on 2 different networks. Issue persists.

I have tried the "calendar not syncing" fixes. No luck.

I forgot to mention that I did spend 2 hours on the phone with an adviser, and after gathering up a lot of information (screen captures/etc) the issue was escalated from there. I haven't heard back yet and it's not resolved. It's a holiday week though so I will be patient.

I am in exactly the same position. On Monterey 12.1, have tried all the 'calendar not syncing' fixes and have deleted the calendar cache multiple times, but have not found a solution.