Thanks for the testing.
We still have some options to try. The next most likely blocker on this Windows profile is an Office-wide policy or experiment override under the Common keys that suppresses Focused Inbox in Classic Outlook. Clearing those per-user policy and experiment keys is a targeted fix that often brings the Show Focused Inbox command back immediately on the View tab.
Close Outlook. Press Windows key + R, type regedit, then press Enter.
In Registry Editor go to HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Common. If you see subkeys named Privacy or Cloud, select Common, choose File > Export to back it up, then delete the Privacy and Cloud subkeys.
Still under HKEY_CURRENT_USER, also browse to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\ExperimentConfigs\Outlook. If ExperimentConfigs exists, export the Outlook key, then delete the Outlook key so any feature flight or override that could be hiding Focused Inbox is removed.
Now check the machine-wide policy path HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Office\16.0\Common and, if present, back up and delete Privacy or Cloud there as well.
If your Office is 32-bit on 64-bit Windows, repeat that machine-wide check under
HKEY_LOCAL_MACHINE\Software\WOW6432Node\Policies\Microsoft\Office\16.0\Common.
Close Registry Editor, restart Windows, open Classic Outlook directly to the Inbox of your Outlook.com account, wait a minute on that folder, then open View > Focused Inbox. The Show Focused Inbox command should render normally and the Focused and Other tabs should appear.
If the panel is still blank after this exact cleanup, tell me and I will move you to the next step.