It’s not so much writer’s block as writer’s gap:

We have all been there, and it feels like end of the world. It’s like a little chickadee being hit by an H-bomb. Here’s the thing, though, I no longer think of it as block. I think that is looking at the problem from the wrong angle. If your wife locks you out of the house, you don’t have a problem with your door.

The word block suggests that you are constipated or stuck, when the truth is that you’re empty.

Lamott, Bird by Bird, page 177

Meaning, you don’t have anything to say. To which you have only two responses: start writing about anything, and see if something emerges. Or get away from your desk and do something else that will fill you up.