You weren't blocked from advancing, this is how people are when they start meditating, their soul reminds them that you have this, this and this problems that you have to fix (like illnesses) then you advance spiritually, and when you are strong enough you start fixing them. If you can't visualize the light for cleaning then use physical feeling like when you are in front of the Suns rays, feeling the warm feeling around your self and you can use the mantra of the Sun Surya, Raum to rise your energies and programming it to clean your aura and chakras, for this you don't need to visualize just vibrate in yourself and affirm while concentrating on yourself. 9x 18x 27x are good vibrations for beginners. Use number 7 for affirmations, thats for cleanliness. And sit with your face and front of your body in the direction of east for better effects. For aphantasia empower the back extension of the 6th chakra as was said.
For advancement widouth visualization you can do Hata Yoga and Kundalini Yoga, Yogic breathing exercises...
Have success and good luck.