Let R(T ) be the error term in Weyl's law for the (2l + 1)-dimensional Heisenberg manifold (H l /Γ, g l ). In this paper, several results on the sign changes and odd moments of R(t) are proved. In particular, it is proved that for some sufficiently large constant c, R(t) changes sign in the interval [T, T +c √ T ] for all large T . Moreover, for a small constant c 1 there exist infinitely many subintervals in [T, 2T ] of length c 1 √ T log −5 T such that ±R(t) > c 1 t l−1/4 holds on each of these subintervals.