Cannot delegate or add people to calendar

Hello RiboflavinB2,

Please check out the information in the following link to ensure the correct process is being used to give another person access to your calendar account, and that the requirements are met, so we can rule out an issue there: Share calendar accounts on Mac

Share calendar accounts on Mac

Share your calendar account with people who use the same CalDAV or Exchange calendar service (for example, with fellow employees at your company). You can choose whether others can edit the calendar account or only view it.

Give another person access to your calendar account

1. In the Calendar app  on your Mac, choose Calendar > Settings, then click Accounts.

2. Select the calendar account.

3. Click Delegation, click Edit, then click the Add button .

4. Enter the name of the person you want to give access to, then choose his or her name from the list that appears.

* If you’re giving access to a CalDAV account, select the Allow Write checkbox to let the person edit your calendars.

* If you’re giving access to an Exchange account, select the person’s level of access from the Calendars column.

If you need additional assistance, please contact Apple Support for help. You may be able to reach them here: Get Support

Thanks!

Hello RiboflavinB2,

Thank you for the update.

You can find the steps for doing this on an iPhone here: Share iCloud calendars on iPhone - Apple Support

Please review that document and make sure everything is correct on your device. If that article doesn’t help, can you tell us exactly what happens when you try to add someone to the calendar. Also, let us know if the same thing happens when trying to add people to a different calendar within the app.

Kindest regards.