Firebase Robo Test : doesn't recognize all project file

Hello everyone I am new with using firebase lab test , I am trying to do Robo Test , I already upload apk , but it keep crashing the error it gives me that it didn't recgnize APP file in the project , I already test my app on 3 different physical devices with different API and companies (HTC , Samsung ) .. and it works fine

and here is a full Test issues .

FATAL EXCEPTION: main
 Process: com.example.mol.saherproject, PID: 8122
 java.lang.RuntimeException: Unable to instantiate application com.example.mol.saherproject.settings.APP: java.lang.ClassNotFoundException: Didn't find class "com.example.mol.saherproject.settings.APP" on path: DexPathList[[zip file "/data/app/com.example.mol.saherproject-1/base.apk"],nativeLibraryDirectories=[/data/app/com.example.mol.saherproject-1/lib/arm, /vendor/lib, /system/lib]]
    at android.app.LoadedApk.makeApplication(LoadedApk.java:578)
    at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4680)
    at android.app.ActivityThread.-wrap1(ActivityThread.java)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1405)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5417)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
 Caused by: java.lang.ClassNotFoundException: Didn't find class "com.example.mol.saherproject.settings.APP" on path: DexPathList[[zip file "/data/app/com.example.mol.saherproject-1/base.apk"],nativeLibraryDirectories=[/data/app/com.example.mol.saherproject-1/lib/arm, /vendor/lib, /system/lib]]
    at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
    at android.app.Instrumentation.newApplication(Instrumentation.java:981)
    at android.app.LoadedApk.makeApplication(LoadedApk.java:573)
    ... 9 more
    Suppressed: java.lang.ClassNotFoundException: com.example.mol.saherproject.settings.APP
        at java.lang.Class.classForName(Native Method)
        at java.lang.BootClassLoader.findClass(ClassLoader.java:781)
        at java.lang.BootClassLoader.loadClass(ClassLoader.java:841)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:504)
        ... 12 more
    Caused by: java.lang.NoClassDefFoundError: Class not found using the boot class loader; no stack trace available

any help please ...