MS Outlook Version 16.16 doesn't show calendar event reminders
The Mac version of Outlook actually has an app that is in charge of displaying/sounding reminders, so it is nothing that you can access outside of Outlook.

If you launch Outlook and go to the Outlook menu the fourth item down should say either "Turn off reminders," or "Turn on reminders."

If it is the former you may want to reinstall Outlook as something has happened to cause the reminder application to not work. If it is the latter... well, problem solved.