1. Krsna is not manifested to everyone.
Chapter 7 Text 25-26
Krsna is not manifested to everyone.

2. nähaà prakäçaù sarvasya müòho ’yaà näbhijänäti
Text 25
nähaà prakäçaù sarvasya
yoga-mäyä-samävåtaù
müòho ’yaà näbhijänäti
loko mäm ajam avyayam
I am never manifest to the foolish and unintelligent. For them I am covered by My internal potency, and therefore they do not know that I am unborn and infallible.

3. Krsna is covered by Yoga-Maya
Krsna was not manifest to everyone even when he was present on this earth. E.g. Duryodhana considered Him ordinary magician. E.g. Shishupal blasphemed Him. E.g. even Brahma, Shiva and Indra were bewildered though devotee.
muhyanti yat sürayaù “By Him even the great sages and demigods are placed into illusion”.

4. Lord Brahma’s prayer
“O Supreme Personality of Godhead, O Supersoul, O master of all mystery, who can calculate Your potency and pastimes in this world? You are always expanding Your internal potency, and therefore no one can understand You. Learned scientists and learned scholars can examine the atomic constitution of the material world or even the planets, but still they are unable to calculate Your energy and potency, although You are present before them.”

5. Text 26 vedähaà samatétäni vartamänäni cärjuna bhaviñyäëi ca bhütäni
mäà tu veda na kaçcana
O Arjuna, as the Supreme Personality of Godhead, I know everything that has happened in the past, all that is happening in the present, and all things that are yet to come. I also know all living entities; but Me no one knows.

6. Form of Krsna is not material
Change of body brings forgetfulness.
Krsna does not forget anything; bahüni me vyatétäni janmäni tava cärjuna täny ahaà veda sarväëi na tvaà vettha parantapa “Many, many births both you and I have passed. I can remember all of them, but you cannot, O subduer of the enemy!”
Therefore Krsna never changes body, “prakåtià sväm adhiñöhäya sambhavämy ätma-mäyayä - I still appear in every millennium in My original transcendental form.”

7. No one knows Krsna Krsna knows past, present and future.
Krsna remains covered by His Yoga-Maya.
Maya cann’t cover Krsna, but the vision of living entities. E.g. sun and cloud.
Without being Krsna Consious not possible to know Krsna though one may realize Brahman and Paramatma features.