What specific problem did Das Ganu encounter while writing his commentary on the Ishavasya Upanishad, and what was Sai Baba's initial advice?

Das Ganu was composing the 'Ishavasya-Bhavartha-Bodhini' to explain the Upanishad in simple language. According to Chapter 20, while he translated the text word for word, he could not grasp its deep, internal secret, and his mind found no joy in the work. When he took this doubt to Sai Baba in Shirdi, Baba did not explain it himself. Instead, he mysteriously told Das Ganu that the resolution for his doubt would be provided by the maidservant at Kaka's house upon his return.