New tab doesn`t show up on device and emulator

I added this three lines code in the correct way into tabs.ts

import {TjeraPage} from '../tjera/tjera';
private tab4Root: any;
this.tab4Root = TjeraPage;

and added this to the actual tabs.html file

<ion-tab [root]="tab4Root" tabTitle="Tjera" tabIcon="information-circle"></ion-tab>

When using ionic serve I see TjeraPage but it doesnt work on a real device or in emulator. No errors are shown. When clicking on the forth tab in emulator I instead see a blank page clicking the second time on it shows me the background of tab1Root.

Do I have to specify new tabs somewhere else? Somehow it seems that the build ignores the forth tab. Thank you for help