1. Firstly, make sure to check that your documents are set with reminders. This can be done under the Revision settings in the Revision Archive of the manual.
2. Secondly, check that the user has "Remind" access to the document. This can be done under Editor/Review Access under the document's settings.
If the user doesn't have access, please contact your admin, so they can rectify the user's permissions.
Note: Documents can be added to "unread" on publication without having to send reminders, Click on Publish → Under send reminders every → Click on No reminders, show in unread: