Is your Outlook top right corner missing toggle option?
By default, the new Outlook for Windows is enabled for all users with Microsoft Entra accounts and Exchange Online accounts. Do you have an administrator in your organization who does anything to disable it?
If not, try modifying the registry below to enable the trial switch and check if that helps. More information, see: Enable or disable access to the new Outlook for Windows | Microsoft Learn.
Hope this helps!
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