Androidx Navigation icon compatability issues in Android 7

I am using com.google.android.material.appbar.AppBarLayout along with androidx.appcompat.widget.Toolbar in my app and in Android 8 it works perfectly but I am having an issue where the 'hamburger' menu icon and 'back' icons are just displaying as a white block in android 7 even though other menu icons are displayed correctly.

Where the hamburger icon is showing.

And what the back button looks like.

My app bar layout:

<com.google.android.material.appbar.AppBarLayout
        android:id="@+id/activity_drawer_layout_app_bar_layout"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary" />

    </com.google.android.material.appbar.AppBarLayout>

And just setting up the toolbar:

setSupportActionBar ( toolbar )

    actionBar?.setDisplayShowCustomEnabled(true)
    actionBar?.setDisplayShowCustomEnabled(true)
    actionBar?.setDisplayHomeAsUpEnabled(true)
    actionBar?.setDisplayShowHomeEnabled(true)
    actionBar?.setDisplayShowTitleEnabled(true)

from Androidx Navigation icon compatability issues in Android 7