Conflicting Tasks

I am trying to cancel a Teams Meeting.

When I right click on the meeting and choose 'Cancel Meeting' I am getting a Microsoft Outlook alert stating "One or more items in the folder you synchronized do not match. To resolve the conflicts, open the items, and then try this operation again"

I don't know what this message means, why I am getting the message, and I don't know how to open the items.

Help please