Android Workmanger PeriodicWorkRequest API work only once?

public class WatchDogWorker extends Worker {
  private static final String uniqueWorkName = "my.package.name.watch_dog_worker";
  private static final long repeatIntervalMin = 30;
  private static final long flexIntervalMin = 10;

  public WatchDogWorker( @NonNull Context context, @NonNull WorkerParameters params) {
    super( context, params );
  }

  private static PeriodicWorkRequest getOwnWorkRequest() {
    return new PeriodicWorkRequest.Builder(
      WatchDogWorker.class, repeatIntervalMin, TimeUnit.MINUTES, flexIntervalMin, TimeUnit.MINUTES
    ).build();
  }

  public static void enqueueSelf() {
    WorkManager.getInstance().enqueueUniquePeriodicWork( uniqueWorkName, ExistingPeriodicWorkPolicy.KEEP, getOwnWorkRequest() );
  }

  public Worker.Result doWork() {
    // Put the actual code of the watchdog that needs to be run every 30mins here
    return Result.SUCCESS;
  }
}

public class BootCompleteReceiver extends BroadcastReceiver {
  public void onReceive( Context context, Intent intent ) {
    if( intent.getAction() == null || !intent.getAction().equals( "android.intent.action.BOOT_COMPLETED" ) ) return;
    WatchDogWorker.enqueueSelf();
  }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  package="...">

  ...

  <application>
    ...
    <receiver
      android:name=".BootCompleteReceiver"
      android:enabled="true"
      android:exported="true">
      <intent-filter>
        <action android:name="android.intent.action.BOOT_COMPLETED"/>
      </intent-filter>
    </receiver>
  </application>
</manifest>

public class MainActivity extends AppCompatActivity {
  ...
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ...

    // Schedule WatchDogWorker (after a fresh install we must not rely on the BootCompleteReceiver)
    WatchDogWorker.enqueueSelf();
  }
}

val oneTimeADayReq: PeriodicWorkRequest = PeriodicWorkRequest.Builder(
        StepCountNotificationWorker::class.java, 
        PeriodicWorkRequest.MIN_PERIODIC_INTERVAL_MILLIS,
        TimeUnit.MILLISECONDS).build()

final PeriodicWorkRequest pwr = new PeriodicWorkRequest
        .Builder(MyWorker.class, 16, TimeUnit.MINUTES)
        .setConstraints(Constraints.NONE)
        .build();

WorkManager.getInstance().enqueueUniquePeriodicWork(
    "my_worker",
    ExistingPeriodicWorkPolicy.REPLACE,
    pwr);