dynamically instantiating classes scala

I am writing a program and as a requirement need to get all of the classes in a package, and need to return objects of them.

I have this code:

  package object cards {
  private val reflections: Reflections = new Reflections(
    new ConfigurationBuilder()
      .setUrls(ClasspathHelper.forPackage("me.mysterymystery.duelingfactions.apiv2.guiindependant.card.cards"))
      .setScanners(new SubTypesScanner())
  )

  def getAllCards: Seq[Card] = reflections.getSubTypesOf(classOf[Card]).asScala.map(_.newInstance()).toSeq
   ...
  }

But get java.lang.NoSuchMethodException: me.mysterymystery.duelingfactions.apiv2.guiindependant.card.MonsterCard.<init>()

Does anybody have any ideas as to why and how to fix it?