Using New Outlook on Windows for personal email, calendar, and contact management
To better understand the issue, could you please confirm whether the Accept, Tentative, and Decline buttons are missing from meeting invitations you receive from other people, or from appointments you create yourself? These response options normally appear for meeting invitations, not personal appointments. Also, does this happen with every meeting invitation or only certain ones? If possible, please share a screenshot of an affected invitation with any personal information hidden.
Additionally, what type of email account are you using in New Outlook (Outlook.com, Microsoft 365, Gmail, or another provider)? Could you also check whether the same meeting invitation displays the response buttons when accessed through your email provider's web interface? This will help determine whether the issue is specific to New Outlook or related to how the invitation is being received or processed.