What was the "Ishavasya-Bhavartha-Bodhini" that Das Ganu was working on, and why was it so challenging for him?

The "Ishavasya-Bhavartha-Bodhini" was a commentary and explanation of the Ishavasya Upanishad that Das Ganu had undertaken. As detailed in Chapter 20, his noble intention was to make this profound scripture accessible to people who were ignorant of the Sanskrit language by translating and explaining its meaning in simple Prakrit Ovi verses. The challenge, however, was immense because the Upanishad is "full of deep meanings." Although Das Ganu was able to perform a word-for-word translation, he found that he couldn't penetrate the "internal secret" or the true, profound essence of the text, which left his mind unsatisfied and prompted him to seek Sai Baba's guidance.