What specific challenge did Das Ganu face while working on the Ishavasya Upanishad, and how did Sai Baba propose to solve it in Chapter 20?

According to Chapter 20, Das Ganu was writing a commentary called "Ishavasya-Bhavartha-Bodhini" to explain the meaning of the Ishavasya Upanishad in simple language for those who didn't know Sanskrit. Although he translated it word for word, he felt his mind found no joy because he couldn't grasp the "internal secret" or deep meaning of the scripture. Faced with this doubt, he went to Shirdi to seek help from Sai Baba. Instead of explaining it himself, Baba gave him a surprising instruction. He told Das Ganu that the resolution to his doubt would be provided by a maidservant at Kaka’s house upon his return.