Dropping some leaves is not terminal, dropping more than half the leaves means something is going wrong. Perhaps your cuttings were from a tree that already had a pest like spider mites or false mites. They are tiny enough that often we don't notice low level infestations.
If humidity is too low, cuttings will fail. I often use a plastic bag. Just set the pot with the cuttings into a plastic bag, seal it, and set the back in bright shade. When you see growth inside the bag, you can begin opening the bag up.