Hi,@Nicholas
Thanks for posting your question in the Microsoft Q&A forum.
Based on your description, when you want to book a meeting, Calendar Assistant does not automatically reject conflicting meeting requests if there is a conflict.
You can achieve this by the following method:
1.Connect to Exchange Online by using remote PowerShell.
2.Run the following command:
Get-CalendarProcessing -Identity "Meeting Room" | Set-CalendarProcessing -AllRequestOutOfPolicy $False
If my answer is helpful to you, please mark it as the answer so that other users can refer to it. Thank you for your support and understanding.