Android elevation property not working

Make sure that the background for the container holding the FrameLayout is not transparent.

According to this Z = Elevation + TranslationZ

so try this:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:card_view="http://schemas.android.com/apk/res-auto"
  android:id="@+id/panel_card"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:background="#ffffff"
  android:elevation="4dp"
  android:translationZ="4dp">