Using Classic Outlook on Windows for personal email, calendar, and contact management
Hi Pat_Fernandez,
Thank you for posting. May I know how did external send the calendar invites, is it generated from Outlook desktop or any other application?
You may check whether you can manually set the reminder, On the Outlook go at the bottom of the screen, click Calendar. Open the meeting. On the Meeting Occurrence tab, on the Option tab click the Reminder dropdown and select how long before the meeting you want to get a reminder. This only applies to the selected meeting in the calendar.
You may refer to the article to check the detailed steps under Add or remove reminders for meetings
Moreover, if the above is not your scenario or I have misunderstood anything, please correct me and provide us with detailed example screenshot information about the issue including the Outlook desktop version via the private message so that we can check to further assist you.
I have sent you private message and here is the link to access it: https://answers.microsoft.com/en-us/privatemessage/inbox
Your patience and cooperation are highly appreciated.
Best regards,
Shyamal