What specific challenge did Das Ganu encounter while working on the Ishavasya Upanishad, and what was Sai Baba's initial advice?

Chapter 20 of the Sai Satcharitra details that Das Ganu was writing a commentary called "Ishavasya-Bhavartha-Bodhini" to explain the scripture in simple language. Although he translated it word for word, he found that he could not grasp the internal secret or deep meaning, which left his mind without joy. When he brought this doubt to the feet of the Satguru in Shirdi, Sai Baba's response was that the resolution to his doubt would be provided by a maidservant at Kaka's house upon his return, setting the stage for a unique teaching.