Search Tab keeps disappearing even if I enable it in Ribbon customisation

I'm using Outlook 365 and the search bar is in the top bar of the Window. When you click it, the search tab appears on the Ribbon. This tab auto-disappears from the ribbon after searching. I have checked in the Ribbon customisation menu and it is shown... if I turn it off and on then when I click OK I see it appear very briefly in the ribbon before disappearing again.

Is this just how Outlook works now or can I force it to always be there?

I'm using Outlook 365 and the search bar is in the top bar of the Window. When you click it, the search tab appears on the Ribbon. This tab auto-disappears from the ribbon after searching.

This is normal behavior for Outlook and the Search Icon on the Ribbon bar.

Two things:

(1) The Ribbon adjusts the icons it displays automatically. That is how Outlook was designed. You can reduce the number of unused icons if you wish. This allows other icons to stay without moving around or disappearing. I do this.

Right click in the Ribbon, choose Customize and in the dialogue box that comes up, you can add and remove icons to suit how you work.

(2) In the same Customize Ribbon dialogue box, left side, default is Popular Commands, and you can change that to All Commands. Search is in the All Commands list.

You can try adding the Search Icon. The Outlook Search bar and Icon are a programmed part of Outlook, so I am not certain this will work.

As I noted, the behavior you see is normal for Outlook 365 fully updated.