Why does my Searchview doesn't display the queryHint in android using androidx?

I have a searchView in the Toolbar which also has Gridview elements. Everything works fine except the queryHint doesn't get displayed in the searchView. I have tried setting android:iconifiedByDefault="false" but the issue persists. Below is the code of activity's layout.

firstscreen.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    tools:context=".ui.activities.FirstScreen">

    <!-- android:numColumns=2 is the number of columns for Grid View
         android:horizontalSpacing is the space between horizontal grid items -->
    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toTopOf="@id/bottomNavigationView"
        app:defaultNavHost="true"
        app:navGraph="@navigation/nav_graph" />

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:background="@color/bottomNavigation"
        android:id="@+id/bottomNavigationView"
        android:layout_width="match_parent"
        android:layout_height="66dp"
        app:layout_insetEdge="bottom"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:menu="@menu/bottom_navigation_menu"/>
</androidx.constraintlayout.widget.ConstraintLayout>

And this is my fragment's xml layout where the searchview is added.
fragment_user.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <!-- Add the Toolbar -->
    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@drawable/flash_tablebar"
        android:title="Lingo"
        android:titleTextColor="@color/new_design_darker_shade">

        <androidx.appcompat.widget.SearchView
            android:id="@+id/searchView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginStart="50dp"
            android:layout_marginEnd="40dp"
            android:layout_marginTop="20dp"
            android:layout_marginBottom="10dp"
            android:background="#FFFF"
            android:queryHint="Search..."
            android:textColorHint="@android:color/black"
            android:iconifiedByDefault="false"/>
    </androidx.appcompat.widget.Toolbar>

    <!-- NestedScrollView to contain the GridView and make it scrollable -->
    <androidx.core.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:fillViewport="true">

        <!-- Your GridView -->
        <GridView
            android:id="@+id/mainSpecimens"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="?android:actionBarSize"
            android:clipToPadding="false"
            android:horizontalSpacing="6dp"
            android:numColumns="3"
            android:verticalSpacing="6dp" />
    </androidx.core.widget.NestedScrollView>
</LinearLayout>

you should change tag of queryHint and iconifiedByDefault form android to app.

app:queryHint="Search..."

app:iconifiedByDefault="false"