Hey, @Rachael07! This sounds frustrating - I’m sorry!

Have you checked to make sure that your future O365 calendar events are marked as “busy”? Alternatively, on your calendar connections page in Calendly, if you click “edit” next to your calendar, there should be an option to mark which statuses are considered conflicts, including “tentative,” “away/out of office” and “working elsewhere.” 

If you haven’t done this and your O365 calendar events have those statuses, they would not be marked as conflicts. Additionally, it’s possible that your future/upcoming events are on a sub calendar that you haven’t selected to be checked for conflicts (this is also possible by clicking “edit” next to your “check for conflicts” calendar): 

Lastly - Calendly can only connect to calendars that you have permission to edit. If you have read-only access to an Office 365 calendar, Calendly cannot connect to it. This means that if you have upcoming events on your calendar that others added for you/invited you to, it’s possible Calendly might not be able to read those as conflicts. For more details, view Microsoft's Share an Outlook Calendar with other people. (In this case, you can either request editing permissions, or, you can manually create another event at the same time and make sure it’s marked “busy” so Calendly picks it up!) 

You can read more about how to properly set up your O365 calendar sync here. I hope that this helps - but let us know in the comments if you are still getting stuck!