Hello Eliot,
First, I want to confirm if you are using Outlook 2016 client or
Outlook Web App(OWA)? It is a normal behavior that after you “Accept” or “Decline” the meeting, the invitation email will be missing in the Inbox folder. You can find the response email in the sent email folder. However, the event you accepted or declined
should be displayed in your calendar.
In order to narrow down the issue and help you resolve the issue, I need to collect some information for further check:
1. Double check if the response email was sent out successfully. Please capture a screenshot if it was sent out.
2. Sign in OWA and see if you can find the event in the calendar. If it shows in OWA but doesn’t show in Outlook 2016 client, please capture screenshots to let me see the difference.
Moreover, I want to know if other users in your organization send you a meeting invitation, and you click Accept or Decline it, you still cannot view it in the calendar? Please feel free to post back if you have any updates.
Regards,
Rick