I delete all the edges you had and highlight these two

Press "C" to get a centered connecting edge

With the edge highlighted I choose "bevel" and create a center face

Now I create this centered edge

I bevel it to crete the highlighted face and shift toward the base of the calculator a bit

With the new edges highlighted I press "4" to divide each with three verts. With verts highlighted "C" connects them with new edges

Create center edges across the four new faces

Bevel to get faces for the keys