I'm unable to share my calendar with others. I get a pop-up message saying "Due to account maintenance, Calendar will be unavailable for a few hours." But that error continues to pop up days after I began trying to share with a new teammate.

Hi FWMike,

Thanks for posting here in Apple Support Communities. The first thing we'd like to have you check is if the software is updated on the device you're using as this may help to address the issue you're facing. Are you able to try sharing calendar from a different device?

Let's also make sure that you restart your device and let us know if that helps. See: Share a calendar on iCloud.com - Apple Support

Kind regards.

I am having the same issue and wonder if this problem has been addressed. I have tried on iOS (iPhone), iPadOS, and MacOS. Recipients are not receiving invitations to my Shared Calendar from the iOS and iPadOS devices. When I use iCloud (Safari Browser) on my MacBook Pro, the error message mentioned above appears. (All devices have latest OS)