Why do Modified outlook meetings get canceled?

I have a similar issue, as an event owner. I modified several events by changing the invitation list (removing someone who did not reply, and adding two new people). O365 sent meeting cancellations to some (but not all) of the people who orginally replied "Yes," as well as the people who declined. The people who had not replied received modified events. 

Is the safest way to make sure the modified event gets on everyone's calendar to delete it entirely and create a new event?

Hello Mitchell94,

Sorry for the delay reply. I am helping @Rudy to monitor this thread. I noticed that you have removed the mobile device from OWA and asked your admin to turn on your Calendar Assistant, may I confirm if your problem still exists?

Best Regards,

Sylvie

Hello Randy954,

I tested on my side based on your description, when I edit an event on calendar, the attendees (no matter who replied “yes” or “decline”) received modified events. No one received cancelation emails. Given this situation, if you use Outlook for Mac client, I would suggest you try to edit events on Outlook Web App to rule out Outlook client problems.

If the problem persists on OWA, as your situation is not the same as this thread, to better help you, we strongly recommend you post a new thread on our forum with your detailed information. There will be another engineer help you troubleshoot your problem more accurately. This can help other community members who have similar problem easily view this thread either.

We truly appreciate your understanding and cooperation.

Best Regards,

Sylvie

Hello Mitchell94,

We haven’t heard back from you. Do you have any updates?

Best Regards,

Sylvie

hi all,

sorry, been a bit busy at work. no, the issues still happen even with the mobile removed on my account. In regards to editing events on my side, I never do that. the events always get modified by the project manager. I rarely ever make meetings to need to modify them.. I am not using the Mac email/calendar client anymore, I am using the official outlook Mac app.

I have no idea why I would need to make a new thread. I find it incredible that nobody was able to figure out my issue still. I am still experiencing the exact issue described in the topic title and description of this original post. To explain my issue again: "when the owner of an event makes any sort of change (adding/deleting a member or adding a url), the event gets canceled for me instead of just being modified. The owner even sees that everyone else in the event is still in it but for some reason, it got canceled just for me. any idea why the event gets canceled only for me when a modification occurs to an event?".... this is EXACTLY what is still happening.