DeviceWatcher Updated and Removed events never fire

I am trying to use a DeviceWatcher to listen for a usb device. If the device is plugged in when my app starts, the Added event fires just fine and I can connect. But if I plug the device in after my app starts, or if I unplug the device, no other events fire. I have added callbacks to Added, Removed, and Updated, which is what the documentation said needed to have callbacks for the thing to work. What am I missing?

private void Watcher_DeviceAdded(DeviceWatcher sender, DeviceInformation deviceInfo) {

    // Watcher may have stopped while we were waiting for our chance to run.
    if (IsWatcherStarted(sender)) {
        _resultCollection.Add(deviceInfo);
        RaiseDeviceChanged(sender, deviceInfo.Id);
    }
}

private void Watcher_DeviceUpdated(DeviceWatcher sender, DeviceInformationUpdate deviceInfoUpdate) {

    // Watcher may have stopped while we were waiting for our chance to run.
    if (IsWatcherStarted(sender)) {
        // Find the corresponding updated DeviceInformation in the collection and pass the update object
        // to the Update method of the existing DeviceInformation. This automatically updates the object
        // for us.
        foreach (var deviceInfoDisp in _resultCollection) {
            if (deviceInfoDisp.Id == deviceInfoUpdate.Id) {
                deviceInfoDisp.Update(deviceInfoUpdate);
                RaiseDeviceChanged(sender, deviceInfoUpdate.Id);
                break;
            }
        }
    }
}

private void Watcher_DeviceRemoved(DeviceWatcher sender, DeviceInformationUpdate deviceInfoUpdate) {

    // Watcher may have stopped while we were waiting for our chance to run.
    if (IsWatcherStarted(sender)) {
        // Find the corresponding DeviceInformation in the collection and remove it
        foreach (var deviceInfoDisp in _resultCollection) {
            if (deviceInfoDisp.Id == deviceInfoUpdate.Id) {
                _resultCollection.Remove(deviceInfoDisp);
                break;
            }
        }

        RaiseDeviceChanged(sender, deviceInfoUpdate.Id);
    }
}