Messages or Errors Displayed on Chatter Screen for Tasks and Events

Recurring tasks, recurring events, and child events are not supported by Chatter.

Consequently, messages or errors appear on the Chatter screen for these records, and attempts to post will fail.

• The message "Chatter isn't enabled or the user doesn't have Chatter access." is displayed on the Chatter screen. 
• The error "You can't post to proposed events, an individual user's instance of a multi-person event, a recurring series of tasks or events, or an occurrence in a recurring series of tasks or events." is displayed when attempting to post.

There is no workaround to post directly to Chatter for these specific records.

As an alternative, consider posting to the Chatter feed of the record associated with the Related To or Name fields (such as an Account or Opportunity) of the Task or Event.