I read that Das Ganu was working on a project related to an Upanishad. What was this project and what difficulty did he encounter?

Chapter 20 explains that Das Ganu was working on a commentary called the "Ishavasya-Bhavartha-Bodhini." His goal was to create a simple explanation of the Ishavasya Upanishad in the Prakrit language, using Ovi verses, so that it would be accessible to people who were ignorant of Sanskrit. As the chapter states, this Upanishad is full of deep meanings. While Das Ganu managed to do a word-for-word translation, he struggled because he could not understand the "internal secret" or the profound underlying meaning, which resulted in his mind finding no joy or satisfaction in the work. This is the doubt he brought to Sai Baba in Shirdi.