Why can't we see a new moon during the daytime?
"Moonlight" is reflected sunlight. We cannot see the moon unless sunlight is hitting it at an angle that we can see from our relative position on earth.
Whether it is impossible to see the "New Moon" or not is different, as there may still be enough scattered light, slight angle, or even the darker image against a starry sky that would give it a visual image.
A new moon doesn't reflect enough light to be seen during the day.
At new moon, the Moon is between the Sun and the Earth. This means that the Moon is only visible during the day. The Moon is normally seen by sunlight reflected from the Moon's surface. During new Moon very little sunlight is reflected from the surface of the Moon facing the Earth.
Therefore, during a new Moon there is not enough light reflected from the surface of the Moon which is facing the Earth to be visible through the atmosphere.
The Moon is only visible in daytime when enough of the Moon is visible which reflects enough light to be seen through the Earth's atmosphere which is flooded with sunlight.