When configuring activity formatter an adding fields. No changes are reflected in the activity stream. No changes are captured.
The field might have "No audit" attribute. This will need to be removed.
1) Open the dictionary entry of the field you want to see in the activity.
2) Look at the related list "Attributes", find "no Audit" attribute, and click on the "i". Do not click on the work 'no audit'. (see screenshot, click the icon circled in red).
3) When its open, click "delete" (see screenshot)