Unresolvable XML tag in Android Studio

Question

While working on a project in android Studio i encountered a problem with the Relative Layout when i check it says Unresolvable tag and the Relative Layout and all its attributes Edit Text,Image-view etc are all highlighted in red . What could be the problem ?? Code shared below.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".HomeActivity">

    <ImageView
        android:id="@+id/app_logo"
        android:layout_width="300dp"
        android:layout_height="100dp"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="60dp"
        android:src="@drawable/ny_logo"
        />

</RelativeLayout>