If a corn, or really any snake, is young and small it will hide. That's the way they avoid being eaten in the wild until they're big enough to move and defend themselves better.

My corns show this well: the tiny worm I'm 'snake sitting' hides all the time. My two younger corns still like to hide, though they will come out more often now. And my three adult corns are always out just laying around in plain view or cruising the cages. The only time they hide is when they're in shed (which is my hint).

Also, to the OP: you could move that tank higher if you got rid of the light. Corns don't really need lights, and do just fine with one UTH on a thermostat and a house/room that doesn't fall below 69. Just make sure, as with all tanks, that the back and sides are covered and insulated and the screen top is foil treated or plexiglass covered (though the openings left can be larger than for ball pythons).