I would never say an attunement or Reiju never worked; energetically we are all connected. What can happen is that a student is closed to the experience, or to the teacher, or the teacher was not in a whole space when offering it. If that was your experience, try another teacher. You can have as many teachers, and as many Reiju, as you like.

I cannot know without seeing you practise, but the question itself says you are not confident, and confidence is the whole point of the symbols. They were added to the system of Reiki to give people something tangible to draw, say and chant so they could feel the energy. They are there to support you, not to be worried about. Practise what you were taught and let it take you in.

The second symbol and its mantra. In the West it was labelled mental and emotional healing. In Japan the mantra means our natural inclination, and our natural inclination is to be our true self. Its characteristic is harmony: the balance between earth and heaven in which we start to feel what we really are.