answer:You seem to be doing everything right. Partial sun, more than one tree. Here is one fact sheet: (Source ) “The Pawpaw, known to botanists as Asimina triloba, is a small, tropical~looking tree, seldom taller than 25 feet. Grown in full sun, the Pawpaw tree develops a narrowly pyramidal shape with dense, drooping foliage down to the ground level. In the shade it grows tall, with a more open branching habit, horizontally held leaves, and few lower limbs. Shading for the first~year, and sometimes the second, is normally required, and it is for this reason that Pawpaws are almost always found in nature as an understory tree. Although the Pawpaw is capable of fruiting in the shade, optimum fruit yields are obtained in open exposure, with some protection from wind (on account of the large leaves). Plant at least two trees for fruit production, to ensure cross~pollination. Some Pawpaw patches never fruit, because all the trees are actually clonal root sprouts from one original tree. In such cases, the patch may be made to bear fruit by planting new trees in and around it, thus providing cross~pollination. Little Pawpaw trees coming up in a patch are usually root sprouts from larger trees, and do not have a sufficient root system of their own. This is why Pawpaw trees dug up in the wild rarely survive. Perhaps because you are on the coast, the trees are getting salty breezes? Is there an arborist or nurseryman in the neighborhood whom you can question?