Hi @Erwan Tortevois ,
Welcome to our forum!
Does this issue occur in Outlook Web app?
And do you mean that the area in the screenshot you provided are not shown, right?
If so, as i know, Calendar sharing may not be available for your account, or may be limited to people in your organization, depending on your organization settings.
Please check if you are using Microsoft 365 or another email service based on Microsoft Exchange Online. More information: Share your calendar in Outlook on the web.
Hope to help you!
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