Grammar books spell out the following rules to make passive voice from verb roots.
I shall take the example of √ इ।
Rule 1. Add य at the end : इ य।
Rule 2. lengthen the final ई of the root: इ becomes ई।
Rule 3 affix atmanepada affixes.
For 3rd pers. imperfect these affixes are अ prefix and त suffix: अ ई य त।
अ ई य त = ऐयत।This is the correct form for √ इ।
Now let us consider this √ इ with an उपसर्ग ‘प्रति’: प्रति √ इ।
The passive imperfect third person is not प्रति + ऐयत।
It is प्रातीयत।
I request any of my learned friends how one gets the form प्रातीयत।
Many thanks.