As pottiepam says' the graft may have failed.
My grafted Kilmarnock Willow, grown in a pot for years, is like a bonsai and hasn't grown more than a couple of inches above the graft, it's possibly about 12 to 18inches high and didn't start to produce buds until I stopped pruning it two yrs ago.
If it's in a pot you could also try lifting it out and checking if the roots are healthy.