Some actions only show on the Action Detail Report if the Auto-Remind checkbox is marked on the action record.
Users are selected on the Filters tab of the report. This filter considers whether users are selected on the Notify screen connected with the Auto-Remind checkbox on the action record. If users are selected on the Filters tab of the report, the report will only include actions with the Auto-Remind checkbox marked and those users selected on the Notify screen.
If you do not need to filter on users receiving reminders for actions, select "Include all" for Users on the Filters tab.