StreamPlot is not working

After finding the gradient of the scalar field F(x,y)= (x^2 * y^2) + (y^2 * z^2) + (x^2 * z^2) I am trying to get its direction field with StreamPlot which is showing an empty box. I did:

v = Grad[F[x, y], {x, y, z}]
{2xy^2 + 2xz^2, 2x^2y + 2yz^2, 2x^2z + 2y^2z}

direcplot = 
 StreamPlot[{2xy^2 + 2xz^2, 2x^2y + 2yz^2, 2x^2z + 2y^2z}, {x, -5, 5}, {y, -5, 5}]

But this does not show the direction fields. What went wrong?