Calendar invites not saving to calendar - they just open as an attachment to a new email message

Hi, when people send me an email with the option to add to calendar, I click on 'Microsoft Outlook' and then it downloads the calendar file. I then click on the downloaded file and it opens in Microsoft Outlook as an attachment in a new email. I used to be able to just click on it and it would open as a new calendar entry but it won't do that anymore.

I am using Microsoft Outlook version 16.45 for desktop on a Mac. I have a Microsoft 365 Business Standard subscription.

While this has been happening, I have just been adding the calendar invite manually and copying the details from the email into the calendar item which is time consuming.

Any ideas how to fix this?

Thanks!