Ion-map icon not showing on iOS

Ion-map icon is not shown on iOS device after phonegap build. It works in the browser and on android device. This is the code I am using:

<ion-nav-buttons side="right">
 <button class="button button-icon ion-map" ui-sref="reqAuth.map">
 </button>
</ion-nav-buttons>

I also have icon on the left side if that matters

<ion-nav-buttons side="left">
 <button class="button button-icon button-clear ion-navicon" menu-toggle="left">
 </button>
</ion-nav-buttons>

Thanks in advance.