For me, less spam, bots, recycled posts.

I would try app:src or adding

 android {  
   defaultConfig {  
     vectorDrawables.useSupportLibrary = true  
    }  

To your build.gradle

https://stackoverflow.com/questions/40624554/difference-between-appsrccompat-and-androidsrc-in-androids-layout-xml

May be relevent to your issue

deleted by creator

Type package:mine level:error in the text bar and see if any errors are returned.

And what is the path of your image, and how are you placing the image in your xml file? Here is an example of one that works for me with an image that is located in the res/drawable/baseline_arrow_back_24.xml package

  <ImageView
        android:id="@+id/backButton"
        android:layout_width="42dp"
        android:layout_height="42dp"
        android:layout_gravity="start"
        android:layout_centerVertical="true"
        android:src="@drawable/baseline_arrow_back_24"
        android:contentDescription="@string/back_arrow" />

Do any errors show in logcat? You should be able to filter to show errors only.

Is it not showing up in the emulator, or the phone on which the app is downloaded, or both?

Fancy cologne.