What specific challenge did Das Ganu face while working on the Ishavasya Upanishad, and what was Sai Baba's initial advice in Chapter 20?

Chapter 20 details the specific intellectual and spiritual problem faced by Das Ganu. He was creating a commentary, the 'Ishavasya-Bhavartha-Bodhini,' to explain the Upanishad in simple language. While he could translate the text word for word, he found himself unable to grasp the deep 'internal secret' or essence of the scripture, which left his mind without joy. When he presented this doubt to Sai Baba in Shirdi, Baba gave him a cryptic instruction. As the chapter recounts, Baba told him, 'The resolution of this doubt of yours will be done by the maidservant at Kaka’s house When you return there.'