Using classic Outlook for Windows in business environments
Try toggling the Automatically dismiss reminders for past calendar events option. This article shows you where you can locate it on various Outlook versions: https://support.microsoft.com/en-us/office/add-or-delete-notifications-or-reminders-in-outlook-7a992377-ca93-4ddd-a711-851ef3597925#bkmk_notificationsettings