After the Desiderative of jñā 'to know' when preceded by anu , the ātmanepada affix is Not used.,
This is an exception to the last sutra. The desiderative of jna with the prefix anu is not atmanepadi.
This sutra read with sutra 1.3.45 limits the scope of parasmaipada to the transitive, desiderative verb anu-jna. As पुत्रमनुजिज्ञासति 'he enquires after the son.'
Why do we say when preceded by anu? Because otherwise it will take the atmanepada terminations. As धर्म्मम् जिज्ञासते 'he inquires after religion.',