Not working with ConstraintLayout

[mradzinski]

The button does not display neither in the preview of the layout nor at runtime.

<android.support.constraint.ConstraintLayout
    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:background="@color/aztec">

    <io.rmiri.buttonloading.ButtonLoading
        android:id="@+id/button"
        android:layout_width="0dp"
        android:layout_height="45dp"
        android:layout_marginEnd="24dp"
        android:layout_marginStart="24dp"
        android:layout_marginTop="24dp"
        app:BL_text="Test"
        app:BL_textColor="@color/aztec"
        app:BL_textSize="16sp"
        app:BL_backgroundColor="@color/white"
        app:BL_circleColor="@color/white"
        app:BL_circleColorSecond="@color/white_100"
        app:BL_stateShow="normal"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"/>

</android.support.constraint.ConstraintLayout>