As I know, In Outlook for Windows, Focused Inbox is available only for Microsoft 365, Exchange, and Outlook.com accounts. What's your account? Please make sure your account is one of three.
Based on my tests, my current Microsoft 365 account (Version 2307 Build 16.0.16626.20086) displays the Focused Inbox correctly on Windows 11.
Based on the above, please check if the "Show Focused Inbox" option is enabled in View tab, as shown in the below image.
In addition, I found a similar issue: when you use Microsoft 365 account and switch from the Inbox to other folders, such as the Sent Items folder, and then you return to Inbox, the Focused Inbox option disappears. Additionally, the option on the View tab to turn on or off the Focused Inbox also disappears. If it is your issue, please refer to resolution and workaround in the below image:
For more information, please refer to: Focused Inbox disappears when you switch folders in Outlook.
(Note: Serious problems can occur if you modify the registry incorrectly. Before making changes, back up the registry to restore it in case something goes wrong.)
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