Hi,
sometimes a tree refuses to seed. There can be several reasons. Maybe it's a hybrid and cannot produce seed. Maybe it's still too small and the tree is keeping its energies for
root growth.
Sometimes it's an environmental problem, when the conditions around the plant don't give the proper signals (you know, some fruit trees require a number of cold hours for it to produce fruit), or the plant is too stressed to spare energies fruiting.
Sometimes it's just the plant being lazy, precisely for a lack of stress. In this case, you can hit the tree trunk with a baseball bat or something like that to stress the tree and scare it into fruiting.