I am completely flummoxed by this and our very capable IT folks are the same. I created a recurring meeting in TEAMS a couple of years ago. I cannot delete this meeting. When I ‘decline’, it reappears. I recorded my screen to ‘prove’ it.
I have checked every calendar app on every device: native apps, Teams, zoom, MS365, Outlook.
I can uncheck the calendar and it goes away but I need it for other, current Teams meetings.
On the Meetings themselves when you open them do you get the option to select between the occurrences and the series as shown in the screenshots (taken on Team app on iPhone):
I think you will have more luck if you try to delete this recurring event in Outlook. There you should be able to view the series as @JensV suggested and then delete it.
Also: confirm that the calendar where the series exists is your Microsoft calendar. I found one Apple Community forum post where a zombie recurring meeting was because the meeting was on two calendars, one of which was an old Google calendar that the person thought wasn’t being used.
I’m trying to delete within my iOS calendar. It does not appear on Outlook or MS365 or in Teams. (or in Zoom or in Google). It is a mystery for the ages!
In your screenshot, where you see Accept Maybe Decline, I believe you need to choose one of the 3 options presented, and then those options will be replaced with Delete Event. I know, it is annoying that you can’t just delete it without first responding, but I have encountered this before and that was the solution for me.
The next step is to completely remove your Microsoft365 account from your iOS device, restart the device, and then try adding it back – force it to resync your calendar.