The Divine Light is always shining, but not all humans can see it.
The concealment or revelation of the Divine Light shining through Daat does not actually happen in Daat itself.
It only seems that way from the human perspective within Malkuth. The perception of change can only occur in Malkuth.
Humans who become self-giving like the Light become able to see it, and for them the benefits of Daat's Light seem "revealed".
However, humans who remain selfish cannot see it, and for them its benefits seem "hidden".