Your changes cannot be saved because you don’t have permission to modify some or all of the items in this folder

Your changes cannot be saved because you don’t have permission to modify some or all of the items in this folder. Do you want to save a copy of this item in the default folder for the item?

This is an error found when you are trying to add a calendar in Exchange without the proper permissions. There is a difference between adding permissions in Outlook and OWA. If you tried using Outlook, then log in online, remove the old permissions and try this:

I recommend logging in online to the OWA calendar

Click the calendar on the right side bar

Click on “Share” in the upper right corner of the window

Add the mailbox of the person you want to share with and give “can edit” permissions