Ionic cordova button not clickable in IOS Emulator

when I run the application on the browser (chrome or safari) I can click and get the click event gets triggered, but when I run it on the IOS device, either as build or emulator it does not get triggered:

Here is the ts code:

triggerEvent() {

    this.changevar = 'This is a message set easily ';  //does not get changed

    this.openAlertBox();   //does not run

  }

The HTML page is as follow:

<ion-content>
<ion-button ion-button expand="block" (click)="triggerEvent()">Trigger Button</ion-button>

 <h2>{{changevar}}</h2>

</ion-content>