ContentLoadingProgressBar is never shows

You should add style to ContentLoadingProgressBar.

<androidx.core.widget.ContentLoadingProgressBar
android:id="@+id/progress"
android:layout_width="wrap_content"
style="?android:attr/progressBarStyleHorizontal"
android:layout_height="wrap_content"/>

Seems you need a style, for example...

style="?android:attr/android:progressBarStyleHorizontal"

Works for me if I put that anyway, without I never see anything.

Also consider putting it above your content (ie below in the xml)

I had tried this :

<android.support.v4.widget.ContentLoadingProgressBar
        android:id="@+id/address_looking_up"
        style="?android:attr/android:progressBarStyleHorizontal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:visibility="visible" />

But, it didn't work at Android 5.0. Some more details about ContentLoadingProgressbar should be here.

PS: Alright, the attribute of 'style' matters here. Change the style to "?android:attr/progressBarStyleLarge" and it works.

Meanwhile, the display effect of this widget depends on the Theme of your app.